mips: fix typo (IRType/IRTemp)

Fix typo (IRType used instead of IRTemp).


git-svn-id: svn://svn.valgrind.org/vex/trunk@2936 8f6e269a-dfd6-0310-a8e1-e2731360e62c
mips: remove unused macro

Remove unused instance of macro ASM_VOLATILE_CASE(rd, sel).


git-svn-id: svn://svn.valgrind.org/vex/trunk@2937 8f6e269a-dfd6-0310-a8e1-e2731360e62c