drivers: block: Mark the functions as static in skd_main.c

Mark functions skd_skmsg_state_to_str() and skd_skreq_state_to_str() as
static in skd_main.c because they are not used outside this file.

This eliminates the following warnings in skd_main.c:
drivers/block/skd_main.c:5272:13: warning: no previous prototype for ‘skd_skmsg_state_to_str’ [-Wmissing-prototypes]
drivers/block/skd_main.c:5284:13: warning: no previous prototype for ‘skd_skreq_state_to_str’ [-Wmissing-prototypes]
Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/skd_main.c

@@ -5269,7 +5269,7 @@ const char *skd_skdev_state_to_str(enum skd_drvr_state state)
 	}
 }
 
-const char *skd_skmsg_state_to_str(enum skd_fit_msg_state state)
+static const char *skd_skmsg_state_to_str(enum skd_fit_msg_state state)
 {
 	switch (state) {
 	case SKD_MSG_STATE_IDLE:
@@ -5281,7 +5281,7 @@ const char *skd_skmsg_state_to_str(enum skd_fit_msg_state state)
 	}
 }
 
-const char *skd_skreq_state_to_str(enum skd_req_state state)
+static const char *skd_skreq_state_to_str(enum skd_req_state state)
 {
 	switch (state) {
 	case SKD_REQ_STATE_IDLE: