Fix misspellings of "whether" in comments.

"Whether" is misspelled in various comments across the tree; this
fixes them. No code changes.

Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 5829d2a..cf9dada 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -722,7 +722,7 @@
 }
 
 /*
- * is_hugepage_only_range() is used by generic code to verify wether
+ * is_hugepage_only_range() is used by generic code to verify whether
  * a normal mmap mapping (non hugetlbfs) is valid on a given area.
  *
  * until the generic code provides a more generic hook and/or starts