ecryptfs: Remove two pointless NULL checks in ecryptfs_dump_cipher

ecryptfs: Remove two pointless NULL checks in ecryptfs_dump_cipher

Clang warns:

../fs/ecryptfs/debug.c:142:12: warning: address of array 'stat->cipher'
will always evaluate to 'true' [-Wpointer-bool-conversion]
        if (stat->cipher)
        ~~  ~~~~~~^~~~~~
../fs/ecryptfs/debug.c:146:12: warning: address of array
'stat->cipher_mode' will always evaluate to 'true'
[-Wpointer-bool-conversion]
        if (stat->cipher_mode)
        ~~  ~~~~~~^~~~~~~~~~~
2 warnings generated.

Fixes: f50a4a1dc7a0 ("eCryptfs: fixed bug in cipher handling")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>