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/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3d3e2c1..06b2635 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3888,7 +3888,7 @@
  * @root - the root we're allocating for
  * @block_rsv - the block_rsv we're allocating for
  * @orig_bytes - the number of bytes we want
- * @flush - wether or not we can flush to make our reservation
+ * @flush - whether or not we can flush to make our reservation
  *
  * This will reserve orgi_bytes number of bytes from the space info associated
  * with the block_rsv.  If there is not enough space it will make an attempt to