caif: cleanup: remove duplicate checks

"phyinfo" can never be null here because we assigned it an address, so I
removed both the assert and the second check inside the if statement.  I
removed the "phyinfo->phy_layer != NULL" check as well because that was
asserted earlier.

Walter Harms suggested I move the "phyinfo->phy_ref_count++;" outside
the if condition for readability, so I have done that.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Sjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>