iommu/amd: Remove unsued extern declaration amd_iommu_init_hardware()

Commit 2c0ae172 ("iommu/amd: Convert iommu initialization to state machine")
left behind this.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20230802133201.17512-1-yuehaibing@huawei.com


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