KVM: x86 emulator: fix eflags preparation for emulation

We prepare eflags for the emulated instruction, then clobber it with an 'andl'.
Fix by popping eflags as the last thing in the sequence.

Patch taken from Xen (16143:959b4b92b6bf)

Signed-off-by: Avi Kivity <avi@qumranet.com>