mm: fix kunmap_high() comment

Signed-off-by: Li Haifeng <omycle@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/highmem.c

@@ -250,7 +250,7 @@ void *kmap_high_get(struct page *page)
 #endif
 
 /**
- * kunmap_high - map a highmem page into memory
+ * kunmap_high - unmap a highmem page into memory
  * @page: &struct page to unmap
  *
  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called