x86emul: correct VEX.W handling for non-64-bit VPINSRD

x86emul: correct VEX.W handling for non-64-bit VPINSRD

Going though the XED commits from the last couple of months made me
notice that VPINSRD, other than VPEXTRD, does not clear VEX.W for non-
64-bit modes, leading to an insertion of stray 32-bits of zero in case
the original instruction had the bit set.

Also remove a pointless fall-through in VPEXTRW handling, bringing
things in line with VPINSRW.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>