intel/common/block/smm: remove return statements from void functions

To be consistent with other occurrences in soc/intel/common, remove the
return statements of weak void funtions since they are not generally
useful.

Found by the linter.

Signed-off-by: Yuchen He <yuchenhe126@gmail.com>
Change-Id: I3fb8217cfcae65b5dc317458b59aa431f1ccdaef
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73866
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/soc/intel/common/block/smm/smihandler.c

@@ -39,7 +39,7 @@ __weak const struct smm_save_state_ops *get_smm_save_state_ops(void)
 /* Specific SOC SMI handler during ramstage finalize phase */
 __weak void smihandler_soc_at_finalize(void)
 {
-	return;
+	/* no-op */
 }
 
 __weak int smihandler_soc_disable_busmaster(pci_devfn_t dev)
@@ -52,12 +52,12 @@ __weak int smihandler_soc_disable_busmaster(pci_devfn_t dev)
 __weak void mainboard_smi_gpi_handler(
 	const struct gpi_status *sts)
 {
-	return;
+	/* no-op */
 }
 
 __weak void mainboard_smi_espi_handler(void)
 {
-	return;
+	/* no-op */
 }
 
 /* Common Functions */