hwf-x86: add EDX as output register for xgetbv asm block
* src/hwf-x86.c (get_xgetbv): Add EDX as output.
XGETBV instruction modifies EAX:EDX register pair, so we need to mark
EDX as output to let compiler know that contents in this register are
lost.
- Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>