%rip-relative addressing is relative to the first byte of the next instruction,
so we need to add %rip only after we've fetched any immediate bytes.

Based on original patch by Li Xin <xin.li@intel.com>.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Acked-by: NLi Xin <xin.li@intel.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>