MC_CMD_LOOPBACK_PHYXS
EFX_STATIC_ASSERT(MC_CMD_LOOPBACK_PHYXS == EFX_LOOPBACK_PHY_XS);
EFX_STATIC_ASSERT(MC_CMD_LOOPBACK_PHYXS == EFX_LOOPBACK_PHY_XS);
EFX_STATIC_ASSERT(MC_CMD_LOOPBACK_PHYXS == EFX_LOOPBACK_PHY_XS);