iommu/amd: Fix premature break in init_iommu_one()

In init_iommu_one(), when processing IOMMU EFR attributes, the code checks
whether GASUP is enabled. If GASUP is not enabled, the code falls back to
legacy guest IR mode and then breaks out of the switch statement.

This break incorrectly skips the subsequent initialization steps that
follow the GASUP check. These initializations are independent of GASUP
support and must always be performed.

Fix this by replacing the early break with a conditional else block,
ensuring that the XTSUP check is only skipped when GASUP is not available.

Fixes: a44092e326d4 ("iommu/amd: Use IVHD EFR for early initialization of IOMMU features")
Reported-by: Sudheer Dantuluri <dantuluris@google.com>
Tested-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>