fs/ntfs3: Remove unused function wnd_bits

Since the function wnd_bits is defined but not called in any file, it is
a useless function, and we delete it in view of the brevity of the code.

Remove some warnings found by running scripts/kernel-doc, which is
caused by using 'make W=1'.

fs/ntfs3/bitmap.c:54:19: warning: unused function 'wnd_bits' [-Wunused-function].
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3/bitmap.c

@@ -51,11 +51,6 @@ void ntfs3_exit_bitmap(void)
 	kmem_cache_destroy(ntfs_enode_cachep);
 }
 
-static inline u32 wnd_bits(const struct wnd_bitmap *wnd, size_t i)
-{
-	return i + 1 == wnd->nwnd ? wnd->bits_last : wnd->sb->s_blocksize * 8;
-}
-
 /*
  * wnd_scan
  *