cpu/x86 asm: Just use the correct op suffix

LLVM AS doesn't support as much GNU junk extensions, data16/32
is almost never needed in truth if we just use the correct op
suffix. So do that here, fixes clang/llvm builds with the
integrated-as toggled on.

Change-Id: I6095d03d0289b418a49a10f135de5eb0e117cae0
Also-by: Damien Zammit <damien@zamaudio.com>
Signed-off-by: Damien Zammit <damien@zamaudio.com>
Reviewed-on: https://review.coreboot.org/21218
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/cpu/x86/sipi_vector.S

@@ -79,7 +79,7 @@ _start:
 	movl	$(gdtaddr), %ebx
 	sub	$(_start), %ebx
 
-	data32 lgdt (%ebx)
+	lgdtl	(%ebx)
 
 	movl	%cr0, %eax
 	andl	$~CR0_CLEAR_FLAGS, %eax