mmc: meson-gx: fix return value check of mmc_add_host()

mmc: meson-gx: fix return value check of mmc_add_host()

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 which
will call mmc_free_host().

Fixes: 51c5d8447bd7 ("MMC: meson: initial support for GX platforms")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20221108123417.479045-1-yangyingliang@huawei.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>