mmc: atmel-mci: Add missing clk_disable_unprepare()

mmc: atmel-mci: Add missing clk_disable_unprepare()

The error path when atmci_configure_dma() set dma fails in atmci driver
does not correctly disable the clock.
Add the missing clk_disable_unprepare() to the error path for pair with
clk_prepare_enable().

Fixes: 467e081d23e6 ("mmc: atmel-mci: use probe deferring if dma controller is not ready yet")
Signed-off-by: Gu Bowen <gubowen5@huawei.com>
Acked-by: Aubin Constans <aubin.constans@microchip.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250225022856.3452240-1-gubowen5@huawei.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>