drbd: Minor cleanups

 . Update comments
 . drbd_set_{in,out_of}_sync(): Remove unused parameters
 . Move common code into adm_del_resource()
 . Redefine ERR_MINOR_EXISTS -> ERR_MINOR_OR_VOLUME_EXISTS

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/drbd.h b/include/linux/drbd.h
index debb70d..8723f2a 100644
--- a/include/linux/drbd.h
+++ b/include/linux/drbd.h
@@ -172,7 +172,7 @@
 	ERR_RES_NOT_KNOWN	= 158,
 	ERR_RES_IN_USE		= 159,
 	ERR_MINOR_CONFIGURED    = 160,
-	ERR_MINOR_EXISTS	= 161,
+	ERR_MINOR_OR_VOLUME_EXISTS = 161,
 	ERR_INVALID_REQUEST	= 162,
 	ERR_NEED_APV_100	= 163,
 	ERR_NEED_ALLOW_TWO_PRI  = 164,