x86_64: Support r8-r15, xmm8-xmm15 in assembler

Added REX support. The TARGET_REX_SUPPORT should be used during build.

Change-Id: I82b457ff5085c8192ad873923bd939fbb91022ce
Signed-off-by: Dmitry Petrochenko <dmitry.petrochenko@intel.com>
4 files changed