exfat: add Kconfig and Makefile

This adds the Kconfig and Makefile for exfat.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
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: b9d1e2e6265f5dc25e9f5dbfbde3e53d8a4958ac
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/


Change-Id: I8730b0a0eb0d7d55f58cdf79094962540cc8d874
Signed-off-by: lixiang <lixiang@codeaurora.org>