igc: igc_write_phy_reg_gpy: drop premature return

Similar to "igc_read_phy_reg_gpy: drop premature return" patch.
igc_write_phy_reg_gpy checks the return value from igc_write_phy_reg_mdic
and if it's not 0, returns immediately. By doing this, it leaves the HW
semaphore in the acquired state.

Drop this premature return statement, the function returns after
releasing the semaphore immediately anyway.

Fixes: 5586838f ("igc: Add code for PHY support")
Suggested-by: Dima Ruinskiy <dima.ruinskiy@intel.com>
Reported-by: Corinna Vinschen <vinschen@redhat.com>
Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>