configure: fix inline asm checks

Commit 8c893aa3 removed quotes that were required to detect
inline asm:

check_insn armv5te qadd r0, r0, r0
.../test.c:1:34: error: expected string literal in 'asm'
void foo(void){ __asm__ volatile(qadd r0, r0, r0); }

The correct code is:

void foo(void){ __asm__ volatile("qadd r0, r0, r0"); }

Commit message written by Frank Liberato <liberato@chromium.org>

Signed-off-by: Martin Storsjö <martin@martin.st>