mmc_add_host() may return error, if we ignore its return value,
it will lead two issues:
1. The memory that allocated in mmc_alloc_host() is leaked.
2. In the remove() path, mmc_remove_host() will be called to
   delete device, but it's not added yet, it will lead a kernel
   crash because of null-ptr-deref in device_del().

Fix this by checking the return value and goto error path wihch
will call mmc_free_host().

Fixes: a45c6cb8 ("[ARM] 5369/1: omap mmc: Add new omap hsmmc controller for 2430 and 34xx, v3")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221108121316.340354-1-yangyingliang@huawei.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>