mmc: pxamci: fix return value check of mmc_add_host()

mmc: pxamci: fix return value check of mmc_add_host()

mmc_add_host() may return error, if we ignore its return value, the memory
that allocated in mmc_alloc_host() will be leaked and it will lead a kernel
crash because of deleting not added device in the remove path.

So fix this by checking the return value and goto error path which will call
mmc_free_host(), besides, ->exit() need be called to uninit the pdata.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221101063023.1664968-5-yangyingliang@huawei.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>