If phy_read_mmd() fails, the error code stored in 'bmsr' should be returned
instead of 'val' which is likely to be 0.
Fixes: 75f4d8d10e01 ("net: phy: add Broadcom BCM84881 PHY driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>