cpu/x86/smm/smmhandler.c: Get revision using C code

This allows to remove some assembly code.

Tested with QEMU Q35 to still print the revision correctly.

Change-Id: I36fb0e8bb1f46806b11ef8102ce74c0d10fd3927
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44319
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/include/cpu/x86/smi_deprecated.h

@@ -15,6 +15,6 @@ void smm_init_completion(void);
 #endif
 
 /* Entry from smmhandler.S. */
-void smi_handler(u32 smm_revision);
+void smi_handler(void);
 
 #endif