net/tls: handle MSG_EOR for tls_sw TX flow

tls_sw_sendmsg() already handles MSG_MORE, but bails
out on MSG_EOR.
Seeing that MSG_EOR is basically the opposite of
MSG_MORE this patch adds handling MSG_EOR by treating
it as the negation of MSG_MORE.
And erroring out if MSG_EOR is specified with MSG_MORE.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230726191556.41714-2-hare@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>