Sink: Don't sink static allocas from the entry block

CodeGen treats allocas outside the entry block as dynamically sized
stack objects.
R600/SI: Use SGPR_(32|64) reg clases when lowering SI_ADDR64_RSRC

The SReg_(32|64) register classes contain special registers in addition
to the numbered SGPRs.  This can lead to machine verifier errors when
these register classes are used as sub-registers for SReg_128, since
SReg_128 only uses the numbered SGPRs.

Replacing SReg_(32|64) with SGPR_(32|64) fixes this problem, since
the SGPR_(32|64) register classes contain only numbered SGPRs.

Tests cases for this are comming in a later commit.
R600/SI: Handle S_MOV_B64 in SIInstrInfo::moveToVALU()
R600/SI: Handle MUBUF instructions in SIInstrInfo::moveToVALU()