Staging: p9auth: fix dependency/build error

Fix p9auth dependency/build failure.  It needs to depend on
CRYPTO.

p9auth.c:(.text+0x107297): undefined reference to `crypto_alloc_base'
p9auth.c:(.text+0x1073d4): undefined reference to `crypto_destroy_tfm'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Ashwin Ganti <ashwin.ganti@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>