x86, intel_txt: Handle ACPI_SLEEP without X86_TRAMPOLINE

On 32 bits, we can have CONFIG_ACPI_SLEEP set without implying
CONFIG_X86_TRAMPOLINE.  In that case, we simply do not need to mark
the trampoline as a MAC region.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Shane Wang <shane.wang@intel.com>
Cc: Joseph Cihula <joseph.cihula@intel.com>