Generalize lpdc_mdio_regs signals pll_sw_reset, pll_locked and aux_reset
make naming consistent with the merged wr-cores commit a27f660bc5d7a3fdffb2a0a9b92678dd3c0d5b16
The signals in the lpdc_mdio_regs can be generalized for QPLL/CPLL. Their use can be extended (not strictly for use in GTXE1/2) also for other lpdc phy implementations (like GTHE4).