x86emul: make _PRE_EFLAGS() tolerate first argument being 32-bit

x86emul: make _PRE_EFLAGS() tolerate first argument being 32-bit

While this may appear to introduce a truncation issue, the high 32 bits
get zapped already anyway (early in _PRE_EFLAGS() as well as in
_POST_EFLAGS()). Once a subsequent patch switches to use proper 32-bit
EFLAGS operands, we'll in fact end up with more correct code, as that
zeroing of the upper halves will then go away.

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