platform/x86: amd-pmc: Simplify error handling and store the pci_dev in amd_pmc_dev...

platform/x86: amd-pmc: Simplify error handling and store the pci_dev in amd_pmc_dev structure

Handle error-exits in the amd_pmc_probe() to avoid duplication and store
the root port information in amd_pmc_probe() so that the information
can be used across multiple routines.

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sanket Goswami <Sanket.Goswami@amd.com>
Link: https://lore.kernel.org/r/20211130112318.92850-2-Sanket.Goswami@amd.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>