exfat: add misc operations

This adds the implementation of misc operations for exfat.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Git-commit: 772b29cca528fcb21374bb3e597d848779938d16
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Change-Id: I1a472cbba93f6053716e1f9c7ba2e82352eda796
Signed-off-by: lixiang <lixiang@codeaurora.org>