fs/ntfs: remove unused variable attr_len

fs/ntfs: remove unused variable attr_len

This variable isn't used anymore, remove it to skip W=1 warning:

  fs/ntfs/inode.c:2350:6: warning: variable `attr_len' set but not used [-Wunused-but-set-variable]

Link: https://lkml.kernel.org/r/4194376f-898b-b602-81c3-210567712092@linux.alibaba.com
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Anton Altaparmakov <anton@tuxera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>