mfd: asic3: Add missing iounmap() on error asic3_mfd_probe

Add the missing iounmap() before return from asic3_mfd_probe
in the error handling case.

Fixes: 64e8867b ("mfd: tmio_mmc hardware abstraction for CNF area")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220307072947.5369-1-linmq006@gmail.com