PM: sleep: Replace strncmp() with str_has_prefix()

Use str_has_prefix() instead of strncmp() which is less
straightforward in decode_state().

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

kernel/power/main.c

@@ -580,7 +580,7 @@ static suspend_state_t decode_state(const char *buf, size_t n)
 	len = p ? p - buf : n;
 
 	/* Check hibernation first. */
-	if (len == 4 && !strncmp(buf, "disk", len))
+	if (len == 4 && str_has_prefix(buf, "disk"))
 		return PM_SUSPEND_MAX;
 
 #ifdef CONFIG_SUSPEND