[X86] Fix bug in COMISD and COMISS definition in td files

COMISD should receive QWORD because it is defined as
 (V)COMISD xmm1, xmm2/m64

COMISS should receive DWORD because it is defined as
 (V)COMISS xmm1, xmm2/m32

Differential Revision: http://reviews.llvm.org/D11712

llvm-svn: 245551