The mbuf protocol flags get cleared between layers, and also it was discovered
that M_DECRYPTED conflicts with M_HASFCS when receiving ethernet patckets.

Add the proper CSUM_TLS_MASK and CSUM_TLS_DECRYPTED defines, and start using
these instead of M_DECRYPTED inside the TCP LRO code.

This change is needed by coming TLS RX hardware offload support patches.

Suggested by:	kib@
Reviewed by:	jhb@
MFC after:	1 week
Sponsored by:	NVIDIA Networking