drm/rockchip: lvds: Fix an error handling path

'ret' is know to be 0 a this point. Checking the return value of
'phy_init()' and 'phy_set_mode()' was intended instead.

So add the missing assignments.

Fixes: cca1705c

 ("drm/rockchip: lvds: Add PX30 support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/248220d4815dc8c8088cebfab7d6df5f70518438.1619881852.git.christophe.jaillet@wanadoo.fr