can: isotp: restore accidentally removed MSG_PEEK feature

can: isotp: restore accidentally removed MSG_PEEK feature

In commit 42bf50a1795a ("can: isotp: support MSG_TRUNC flag when
reading from socket") a new check for recvmsg flags has been
introduced that only checked for the flags that are handled in
isotp_recvmsg() itself.

This accidentally removed the MSG_PEEK feature flag which is processed
later in the call chain in __skb_try_recv_from_queue().

Add MSG_PEEK to the set of valid flags to restore the feature.

Fixes: 42bf50a1795a ("can: isotp: support MSG_TRUNC flag when reading from socket")
Link: https://github.com/linux-can/can-utils/issues/347#issuecomment-1079554254
Link: https://lore.kernel.org/all/[email protected]
Reported-by: Derek Will <[email protected]>
Suggested-by: Derek Will <[email protected]>
Tested-by: Derek Will <[email protected]>
Signed-off-by: Oliver Hartkopp <[email protected]>
Signed-off-by: Marc Kleine-Budde <[email protected]>