configure: add support for mips32r5, p5600 cpu and msa

Imagination Technologies has come up with MIPS Warrior Processor Cores.
More details can be found at-
http://www.imgtec.com/mips/warrior/pclass.asp
http://www.imgtec.com/mips/warrior/iclass.asp



This is a preparation patch to submit optimized code for MSA (MIPS-SIMD-Architecture)
This patch set is adding support for P5600 and I6400 CPUs.

MIPS 'generic' case is added, with mips32r2 arch as default (fpu and dsp opt enabled).

Sample configurations for new MSA architectures-
    $ ./configure --enable-cross-compile --cross-prefix=<PATH> --arch=mips --target-os=linux --cpu=p5600
    $ ./configure --enable-cross-compile --cross-prefix=<PATH> --arch=mips --target-os=linux --cpu=i6400

Signed-off-by: Shivraj Patil <shivraj.patil@imgtec.com>
Reviewed-by: Nedeljko Babic <Nedeljko.Babic@imgtec.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>