MIPS: microMIPS: uasm: Split 'uasm.c' into two files.

Split 'uasm.c' into two files. The new file 'uasm-mips.c' has the
functions specific to the classic MIPS ISA. The 'uasm.c' file
contains common code that can be used by classic or other ISAs
that could be supported by the kernel.

Signed-off-by: Steven J. Hill <sjhill@mips.com>
Cc: linux-mips@linux-mips.org
Cc: cernekee@gmail.com
Cc: kevink@paralogos.com
Cc: ddaney.cavm@gmail.com
Patchwork: https://patchwork.linux-mips.org/patch/4922/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
(cherry picked from commit 0961103562ab958fa74f35043bf4f72e51ed6155)