Fix MMX rgb24 to yuv conversion with gcc 4.6

When built with gcc 4.6, the MMX rgb24 to yuv conversion gives
wrong output.  The compiler produces this warning:

libswscale/swscale_template.c:1885:5: warning: use of memory input without lvalue in asm operand 4 is deprecated

Changing the memory operand to a register makes it work.

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit f344903c)

libswscale/swscale_template.c

@@ -1883,7 +1883,7 @@ static inline void RENAME(bgr24ToY_mmx)(uint8_t *dst, const uint8_t *src, long w
 static inline void RENAME(bgr24ToUV_mmx)(uint8_t *dstU, uint8_t *dstV, const uint8_t *src, long width, enum PixelFormat srcFormat)
 {
     __asm__ volatile(
-        "movq                    24+%4, %%mm6       \n\t"
+        "movq                   24(%4), %%mm6       \n\t"
         "mov                        %3, %%"REG_a"   \n\t"
         "pxor                    %%mm7, %%mm7       \n\t"
         "1:                                         \n\t"
@@ -1894,9 +1894,9 @@ static inline void RENAME(bgr24ToUV_mmx)(uint8_t *dstU, uint8_t *dstV, const uin
         "punpcklbw               %%mm7, %%mm1       \n\t"
         "movq                    %%mm0, %%mm2       \n\t"
         "movq                    %%mm1, %%mm3       \n\t"
-        "pmaddwd                    %4, %%mm0       \n\t"
-        "pmaddwd                  8+%4, %%mm1       \n\t"
-        "pmaddwd                 16+%4, %%mm2       \n\t"
+        "pmaddwd                  (%4), %%mm0       \n\t"
+        "pmaddwd                 8(%4), %%mm1       \n\t"
+        "pmaddwd                16(%4), %%mm2       \n\t"
         "pmaddwd                 %%mm6, %%mm3       \n\t"
         "paddd                   %%mm1, %%mm0       \n\t"
         "paddd                   %%mm3, %%mm2       \n\t"
@@ -1908,9 +1908,9 @@ static inline void RENAME(bgr24ToUV_mmx)(uint8_t *dstU, uint8_t *dstV, const uin
         "punpcklbw               %%mm7, %%mm3       \n\t"
         "movq                    %%mm1, %%mm4       \n\t"
         "movq                    %%mm3, %%mm5       \n\t"
-        "pmaddwd                    %4, %%mm1       \n\t"
-        "pmaddwd                  8+%4, %%mm3       \n\t"
-        "pmaddwd                 16+%4, %%mm4       \n\t"
+        "pmaddwd                  (%4), %%mm1       \n\t"
+        "pmaddwd                 8(%4), %%mm3       \n\t"
+        "pmaddwd                16(%4), %%mm4       \n\t"
         "pmaddwd                 %%mm6, %%mm5       \n\t"
         "paddd                   %%mm3, %%mm1       \n\t"
         "paddd                   %%mm5, %%mm4       \n\t"
@@ -1933,7 +1933,7 @@ static inline void RENAME(bgr24ToUV_mmx)(uint8_t *dstU, uint8_t *dstV, const uin
         "add                        $4, %%"REG_a"   \n\t"
         " js                        1b              \n\t"
     : "+r" (src)
-    : "r" (dstU+width), "r" (dstV+width), "g" ((x86_reg)-width), "m"(ff_bgr24toUV[srcFormat == PIX_FMT_RGB24][0])
+    : "r" (dstU+width), "r" (dstV+width), "g" ((x86_reg)-width), "r"(ff_bgr24toUV[srcFormat == PIX_FMT_RGB24])
     : "%"REG_a
     );
 }