This tests the following powerdown features:
•TX powerdown (TXPD) in PCIe and SATA mode
•RX powerdown (RXPD) in PCIe and SATA mode
•CPLL powerdown (CPLLPD)
•QPLL powerdown (QPLLPD)
•TX phase and delay aligner powerdown (TXPHDLYPD)
•RX phase and delay aligner powerdown (RXPHDLYPD)