x86: reuse further VEX entries for EVEX

x86: reuse further VEX entries for EVEX

When the VEX.L=1 decode matches that of both EVEX.L'L=1 and EVEX.L'L=2
(typically when all three are invalid) the (smaller) VEX table entry can
be reused by EVEX, instead of duplicating data. (Note that XM and XMM as
well as EXxmm_md and EXd are equivalent at least for the purposes here.)