[AMDGPU] Fixed SIInstrInfo::getOpSize to handle subregs
[AMDGPU] Fixed SIInstrInfo::getOpSize to handle subregs

Currently it returns incorrect operand size for a target independet
node such as COPY if operand is a register with subreg. Instead of
correct subreg size it returns a size of the whole superreg.

Differential Revision: https://reviews.llvm.org/D52736

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@343508 91177308-0d34-0410-b5e6-96231b3b80d8

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