Quick: Fix out of temp regs in ArmMir2Lir::GenMulLong().

This fixes running out of temp registers for mul-long that
needs a temporary to store the result, i.e. when it's stored
to stack location [sp, #offset] with offset >= 1024. The bug
is currently not reproducible because ARM_R4_SUSPEND_FLAG is
off and thus we have the extra register available. However,
the code generation could be cleaned up and make use of that
extra register, so pre-emptively fix it anyway.

Bug: 20110806
Change-Id: I8362c349961dbe28fc3ec8a9299b66fd72f26779