net: phy: micrel: Fixed error related to uninitialized symbol ret

Initialized return variable

Fixes Old smatch warnings:
drivers/net/phy/micrel.c:1750 ksz886x_cable_test_get_status() error:
uninitialized symbol 'ret'.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Divya Koppera <Divya.Koppera@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>