sev-dev.c calls code in the AMD IOMMU now but that can't really work if
latter is not enabled in Kconfig:

  ld: vmlinux.o: in function `__sev_firmware_shutdown.isra.0':
  sev-dev.c:(.text+0x2501f0e): undefined reference to `amd_iommu_snp_disable'
  ld: vmlinux.o: in function `snp_rmptable_init':
  sev.c:(.init.text+0x26260): undefined reference to `amd_iommu_snp_en'
  make[2]: *** [scripts/Makefile.vmlinux:37: vmlinux] Error 1
  make: *** [Makefile:240: __sub-make] Error 2

Fix those deps.

Fixes: f366a8da ("iommu/amd: Clean up RMP entries for IOMMU pages during SNP shutdown")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240207204721.6189-1-bp@alien8.de