tls splice: remove inappropriate flags checking for MSG_PEEK

In function tls_sw_splice_read, before call tls_sw_advance_skb
it checks likely(!(flags & MSG_PEEK)), while MSG_PEEK is used
for recvmsg, splice supports SPLICE_F_NONBLOCK, SPLICE_F_MOVE,
SPLICE_F_MORE, should remove this checking.

Signed-off-by: Jim Ma <majinjing3@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>