mm/sparse: fix a typo in comment "convienence"->"convenience"

There is a typo in comment, fix it.
Signed-off-by: NEthon Paul <ethp@qq.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200411002955.14545-1-ethp@qq.comSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/sparse.c

@@ -288,7 +288,7 @@ void __init memory_present(int nid, unsigned long start, unsigned long end)
 
 /*
  * Mark all memblocks as present using memory_present(). This is a
- * convienence function that is useful for a number of arches
+ * convenience function that is useful for a number of arches
  * to mark all of the systems memory as present during initialization.
  */
 void __init memblocks_present(void)