mips32: Fixed the problem with FCSR register.

Until now, Valgrind has read two registers to calculate FCSR
value. From now on, Valgrind reads exact number of fpu
registers (one or two).


git-svn-id: svn://svn.valgrind.org/vex/trunk@2794 8f6e269a-dfd6-0310-a8e1-e2731360e62c