iommu/amd: Remove unsued extern declaration amd_iommu_init_hardware()

Commit 2c0ae1720c09 ("iommu/amd: Convert iommu initialization to state machine")
left behind this.

Signed-off-by: YueHaibing <[e-mail]>
Reviewed-by: Suravee Suthikulpanit <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Joerg Roedel <[e-mail]>

include/linux/amd-iommu.h

···
 struct pci_dev;
 
 extern int amd_iommu_detect(void);
-extern int amd_iommu_init_hardware(void);
 
 /**
  * amd_iommu_init_device() - Init device for use with IOMMUv2 driver