Fix the missing clk_disable_unprepare() before return
from mt7621_spi_probe in the error handling case.

Fixes: cbd66c62 ("spi: mt7621: Move SPI driver out of staging")
Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Link: https://lore.kernel.org/r/20201103074912.195576-1-miaoqinglang@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>