AmpereAltraPkg: Update Ampere specific platform PCIe core

This patch updates the following:
- Check End Point configuration space is accessible or
  not before getting its capability.
- Add new function to check PCIe card is present or not.
- Set CRS (Configuration Request Retry Status) to follow
  PCIe specifications.

Signed-off-by: Nhi Pham <nhi@os.amperecomputing.com>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>