mmc: octeontx2: finish_dma_single() should teardown/unmap

commit aece27bf436570a72c6bc6932b9eefde0ba46873 from
git@git.assembla.com:cavium/WindRiver.linux.git

Since its introduction, finish_dma_single() has left the
DMA mapping in place, slowly depleting the iommu stream's
address space, and stalling transfers when the pool is empty

Change-Id: I6371f29682cd681d9c86b93de0e9db92c6f0d22d
Signed-off-by: Peter Swain <pswain@cavium.com>
Reviewed-on: https://sj1git1.cavium.com/2240


Reviewed-by: Chandrakala Chavva <Chandrakala.Chavva@cavium.com>
Reviewed-on: https://sj1git1.cavium.com/8541


Tested-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Reviewed-by: Chandrakala Chavva <cchavva@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/26905


Reviewed-by: Sunil Kovvuri Goutham <Sunil.Goutham@cavium.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>