net: gemini: Fix missing clk_disable_unprepare() in error path of gemini_ethernet_port_probe()

Fix the missing clk_disable_unprepare() before return
from gemini_ethernet_port_probe() in the error handling case.

Fixes: 4d5ae32f

 ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>