[mips] Add range checks and transformation to octeon instructions in AsmParser.

This patch adds range checks to the immediate operands of octeon
instructions in the AsmParser. Like gas, it applies the following
transformations if the immediate is to large:

bbit0 $8, 42, foo => bbit032 $8, 10, foo
bbit1 $8, 46, foo => bbit132 $8, 14, foo
cins $8, $31, 32, 31 => cins32 $8, $31, 0, 31
exts $7, $4, 54, 9 => exts32 $7, $4, 22, 9

Reviewed By: dsanders

Differential Revision: http://reviews.llvm.org/D7080

llvm-svn: 227225