[MIPS] Fix several profiling issues caused by incorrect register saves

rTEMP is used by the JAL and JALR macros so it needs to be preserved
if it is holding some other useful value. No need to save ra in rTEMP
if using JAL/JALR macros.

Change-Id: I1bf8c3b044faa944021b4331e0a71c1489b70241
Signed-off-by: Douglas Leung <douglas@mips.com>
Signed-off-by: Chris Dearman <chris@mips.com>