libceph: Fix spelling mistakes

Fix some spelling mistakes in comments:
enconding  ==> encoding
ambigous  ==> ambiguous
orignal  ==> original
encyption  ==> encryption

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>