[NFC][PowerPC] Return early if the element type is not byte-sized in combineBVOfConsecutiveLoads
[NFC][PowerPC] Return early if the element type is not byte-sized in combineBVOfConsecutiveLoads

Summary:
Based on the Eli Friedman's comments in https://reviews.llvm.org/D60811 , we'd better return early if the element type is not byte-sized in `combineBVOfConsecutiveLoads`.

Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D61076


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@359764 91177308-0d34-0410-b5e6-96231b3b80d8

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