net: phy: bcm84881: Fix some error handling paths

If phy_read_mmd() fails, the error code stored in 'bmsr' should be returned
instead of 'val' which is likely to be 0.

Fixes: 75f4d8d1 ("net: phy: add Broadcom BCM84881 PHY driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://patch.msgid.link/3e1755b0c40340d00e089d6adae5bca2f8c79e53.1727982168.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Jakub Kicinski <kuba@kernel.org>