cifsd: fix WARNING: unmet direct dependencies detected for CRYPTO_ARC4

cifsd: fix WARNING: unmet direct dependencies detected for CRYPTO_ARC4

Randy reported warning message from fs/cifsd/Kconfig.

WARNING: unmet direct dependencies detected for CRYPTO_ARC4
  Depends on [n]: CRYPTO [=y] && CRYPTO_USER_API_ENABLE_OBSOLETE [=n]
  Selected by [y]:
  - SMB_SERVER [=y] && NETWORK_FILESYSTEMS [=y] && INET [=y]

arc4 library is not currently in use. So this patch eliminates
unnecessary library set in cifsd.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>