arch/x86: Create helper for APM_CNT SMI triggers

Attempts to write to APM_CNT IO port should always be guarded
with a test to verify SMI handler has been installed.

Immediate followup removes redundant HAVE_SMI_HANDLER tests.

Change-Id: If3fb0f1a8b32076f1d9f3fea9f817dd4b093ad98
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41971
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/cpu/x86/smm.h

@@ -29,6 +29,9 @@
 #define APM_CNT_ELOG_GSMI	0xef
 #define APM_STS		0xb3
 
+/* Send cmd to APM_CNT with HAVE_SMI_HANDLER checking. */
+int apm_control(u8 cmd);
+
 void io_trap_handler(int smif);
 int southbridge_io_trap_handler(int smif);
 int mainboard_io_trap_handler(int smif);