Merge isSHUFPMask and isCommutedSHUFPMask into single function that can do...

Merge isSHUFPMask and isCommutedSHUFPMask into single function that can do both. Do the same for the 256-bit version. Use loops to reduce size of isVSHUFPYMask. Fix test cases that were incorrectly passing due to isCommutedSHUFPMask not checking for the vector being 128-bit. This caused some 256-bit shuffles to be incorrectly commuted.

llvm-svn: 145921