atl1c: refine/update ASPM configuration

some platforms(BIOS or OS) may change ASPM configuration in
PCI Express Link Control Register directly and dynamically
regardless the device driver installation.
Checking if ASPM support during the driver init phase by reading
PCI Express Link Contrl Register doesn't make sense.
This refine/update assume L0S/L1 is defalut enabled as hw->ctrl_flags
inited. atl1c_set_aspm will set real configuration based on chip
capability to hardware register.
atl1c_disable_l0s_l1 and register definition of REG_PM_CTRL are
refined as well.

Signed-off-by: xiong <xiong@qca.qualcomm.com>
Tested-by: Liu David <dwliu@qca.qualcomm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>