mgmt: mcumgr: Make handler registration functions static

Makes group registration functions for MCUmgr handlers static as
they are registered automatically at startup.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

subsys/mgmt/mcumgr/grp/fs_mgmt/src/fs_mgmt.c

@@ -674,7 +674,7 @@ static struct mgmt_group fs_mgmt_group = {
 	.mg_group_id = MGMT_GROUP_ID_FS,
 };
 
-void fs_mgmt_register_group(void)
+static void fs_mgmt_register_group(void)
 {
 	mgmt_register_group(&fs_mgmt_group);
 

subsys/mgmt/mcumgr/grp/img_mgmt/src/img_mgmt.c

@@ -611,15 +611,9 @@ static struct mgmt_group img_mgmt_group = {
 	.mg_group_id = MGMT_GROUP_ID_IMAGE,
 };
 
-
-void img_mgmt_register_group(void)
+static void img_mgmt_register_group(void)
 {
 	mgmt_register_group(&img_mgmt_group);
 }
 
-void img_mgmt_unregister_group(void)
-{
-	mgmt_unregister_group(&img_mgmt_group);
-}
-
 MCUMGR_HANDLER_DEFINE(img_mgmt, img_mgmt_register_group);

subsys/mgmt/mcumgr/grp/os_mgmt/src/os_mgmt.c

@@ -676,7 +676,7 @@ static struct mgmt_group os_mgmt_group = {
 	.mg_group_id = MGMT_GROUP_ID_OS,
 };
 
-void os_mgmt_register_group(void)
+static void os_mgmt_register_group(void)
 {
 	mgmt_register_group(&os_mgmt_group);
 }

subsys/mgmt/mcumgr/grp/shell_mgmt/src/shell_mgmt.c

@@ -135,8 +135,7 @@ static struct mgmt_group shell_mgmt_group = {
 	.mg_group_id = MGMT_GROUP_ID_SHELL,
 };
 
-
-void shell_mgmt_register_group(void)
+static void shell_mgmt_register_group(void)
 {
 	mgmt_register_group(&shell_mgmt_group);
 }

subsys/mgmt/mcumgr/grp/stat_mgmt/src/stat_mgmt.c

@@ -238,7 +238,7 @@ static struct mgmt_group stat_mgmt_group = {
 	.mg_group_id = MGMT_GROUP_ID_STAT,
 };
 
-void stat_mgmt_register_group(void)
+static void stat_mgmt_register_group(void)
 {
 	mgmt_register_group(&stat_mgmt_group);
 }

subsys/mgmt/mcumgr/grp/zephyr_basic/src/basic_mgmt.c

@@ -60,7 +60,7 @@ static struct mgmt_group zephyr_basic_mgmt_group = {
 	.mg_group_id = (ZEPHYR_MGMT_GRP_BASIC),
 };
 
-void zephyr_basic_mgmt_init(void)
+static void zephyr_basic_mgmt_init(void)
 {
 	mgmt_register_group(&zephyr_basic_mgmt_group);
 }