iommu/exynos: Fix error handling in exynos_iommu_init()

If platform_driver_register() fails, it don't need unregister and call
kmem_cache_free() to free the memory allocated before calling register.

Fixes: bbc4d205 ("iommu/exynos: Fix driver initialization sequence")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20230104095702.2591122-1-yangyingliang@huawei.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>