x86/asm: Add _ASM_BYTES() macro for a .byte ... opcode sequence

Make it easy to create a sequence of bytes that can be used in either
assembly proper on in a C asm() statement.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210510090940.924953-3-hpa@zytor.com