x86: honor VEX.W for VCVT{PH2PS,PS2PH}

x86: honor VEX.W for VCVT{PH2PS,PS2PH}

Unlike for the EVEX-encoded versions, the VEX ones failed to decode
VEX.W. Once the necessary adjustments are done, it becomes obvious that
the EVEX and VEX table entries for VCVTPS2PH are identical and can hence
be folded.