net: phy: dp83867: fix simple_return.cocci warnings

drivers/net/phy/dp83867.c:126:1-4: WARNING: end returns can be simpified
drivers/net/phy/dp83867.c:74:5-8: WARNING: end returns can be simpified if tested value is negative or 0

 Simplify a trivial if-return sequence.  Possibly combine with a
 preceding function call.

Generated by: scripts/coccinelle/misc/simple_return.cocci

CC: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>