ext4: fix the comment describing ext4_ext_search_right()

The comment describing what ext4_ext_search_right() does is incorrect.
We return 0 in *phys when *logical is the 'largest' allocated block,
not smallest.  

Fix a few other typos while we're at it.

Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1380cd2..4863238 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -458,7 +458,7 @@
  * the buffer head is mapped.
  *
  * It returns 0 if plain look up failed (blocks have not been allocated), in
- * that casem, buffer head is unmapped
+ * that case, buffer head is unmapped
  *
  * It returns the error in case of allocation failure.
  */
@@ -497,7 +497,7 @@
 	 * Returns if the blocks have already allocated
 	 *
 	 * Note that if blocks have been preallocated
-	 * ext4_ext_get_block() returns th create = 0
+	 * ext4_ext_get_block() returns the create = 0
 	 * with buffer head unmapped.
 	 */
 	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED)