phy: miphy28lp: unlock on error in miphy28lp_init()

We need to unlock before returning the -EINVAL here.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Gabriel Fernandez <gabriel.fernandez@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>