Revert "src: Remove unused include <cpu/x86/smm.h>"

This reverts commit 6f739184dd.

Fixes compiling the SMMSTORE driver.

Change-Id: I3b4d4063ded50529bea48f8d865c1689fe9e26d1
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43970
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Michael Niewöhner
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/drivers/smmstore/smi.c

@@ -2,6 +2,7 @@
 
 #include <console/console.h>
 #include <commonlib/region.h>
+#include <cpu/x86/smm.h>
 #include <smmstore.h>
 #include <stddef.h>
 #include <stdint.h>

src/soc/intel/skylake/romstage/romstage.c

@@ -4,6 +4,7 @@
 #include <arch/symbols.h>
 #include <assert.h>
 #include <cpu/x86/msr.h>
+#include <cpu/x86/smm.h>
 #include <cbmem.h>
 #include <console/console.h>
 #include <device/pci_def.h>