[x86] Fix printing of register operands with q modifier.

Emit 32-bit register names instead of 64-bit register names if the target does
not have 64-bit general purpose registers.

<rdar://problem/14653996>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205067 91177308-0d34-0410-b5e6-96231b3b80d8