cpu/x86/smm: Add SMM_LEGACY_ASEG

Followup will allow use of PARALLEL_MP with SMM_ASEG so
some guards need to be adjusted.

Change-Id: If032ce2be4749559db0d46ab5ae422afa7666785
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61480
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/include/cpu/x86/smi_deprecated.h

@@ -3,16 +3,8 @@
 #ifndef __X86_SMI_DEPRECATED_H__
 #define __X86_SMI_DEPRECATED_H__
 
-#include <stdint.h>
-
-#if CONFIG(PARALLEL_MP) || !CONFIG(HAVE_SMI_HANDLER)
-/* Empty stubs for platforms without SMI handlers. */
-static inline void smm_init(void) { }
-static inline void smm_init_completion(void) { }
-#else
 void smm_init(void);
 void smm_init_completion(void);
-#endif
 
 /* Entry from smmhandler.S. */
 void smi_handler(void);