sparse: fix comment

retmain -> remain

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/mm/sparse.c b/mm/sparse.c
index 63c3ea5..38cad8f 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -268,7 +268,7 @@
 	/*
 	 * A page may contain usemaps for other sections preventing the
 	 * page being freed and making a section unremovable while
-	 * other sections referencing the usemap retmain active. Similarly,
+	 * other sections referencing the usemap remain active. Similarly,
 	 * a pgdat can prevent a section being removed. If section A
 	 * contains a pgdat and section B contains the usemap, both
 	 * sections become inter-dependent. This allocates usemaps