MIPS: dsp: Support toolchains without DSP ASE and microMIPS.

Add macros to support the DSP ASE with microMIPS kernels when the
toolchain does not have support.

Signed-off-by: Steven J. Hill <sjhill@mips.com>
Patchwork: http://patchwork.linux-mips.org/patch/4686/


Signed-off-by: John Crispin <blogic@openwrt.org>