Fix Neon intrinsic immediate range checking for some double-register operands.

Some quad-register intrinsics with lane operands only take a double-register
operand for the vector containing the lane.  The valid range of lane numbers
is then half as big as you would expect from the quad-register type.
Note: This currently has no effect because those intrinsics are now handled
entirely in the header file using __builtin_shufflevector, which does its own
range checking, but I want to use this for generating tests.

llvm-svn: 121867