net/tls: pass context to tls_device_decrypted()

Avoid unnecessary pointer chasing and calculations, callers already
have most of the state tls_device_decrypted() needs.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>