Revert "OpenCL: handle shift operator with vector operands"

This reverts commit r228382.

This breaks the following case:  Reported by Jeroen Ketema:
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20150202/122961.html

typedef __attribute__((ext_vector_type(3))) char char3;

void foo() {
 char3 v = {1,1,1};
 char3 w = {1,2,3};

 w <<= v;
}

If I compile with:

 clang -x cl file.c

Then an error is produced:

file.c:10:5: error: expression is not assignable
 w <<= v;
 ~ ^
1 error generated.

llvm-svn: 228406