configure, mips: remove MIPS32R2, merging it with MIPSFPU

There are no independant uses of mips32r2 instructions except for the
FPU parts. Due to the heavy use of mips32r2 specifc fpu extensions, I
am guessing the original author intended MIPSFPU to imply MIPS32R2 anyway.

Since these fpu instructions are available on mips64 (non-r2), enable them
there as well.

Also remove the last occurence of HAVE_MIPS32R2 (which is coupled to
HAVE_MIPSFPU anyway).

mips32r2 is left in the list of options form compatability so that using
--disable-mips32r2 doesn't break anything.

Signed-off-by: James Cowgill <james410@cowgill.org.uk>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>