platform-drivers-x86: dell-laptop: Remove unneeded mutex_init() for buffer_mutex

DEFINE_MUTEX() will automatically initialize buffer_mutex,
no need to call mutex_init() in dell_init().

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/dell-laptop.c

@@ -612,7 +612,6 @@ static int __init dell_init(void)
 	if (!bufferpage)
 		goto fail_buffer;
 	buffer = page_address(bufferpage);
-	mutex_init(&buffer_mutex);
 
 	ret = dell_setup_rfkill();