PCI/ASPM: Fix L1 substate handling in aspm_attr_store_common()

PCI/ASPM: Fix L1 substate handling in aspm_attr_store_common()

aspm_attr_store_common(), which handles sysfs control of ASPM, has the same
problem as fb097dcd5a28 ("PCI/ASPM: Disable only ASPM_STATE_L1 when driver
disables L1"): disabling L1 adds only ASPM_L1 (but not any of the L1.x
substates) to the "aspm_disable" mask.

Enabling one substate, e.g., L1.1, via sysfs removes ASPM_L1 from the
disable mask.  Since disabling L1 via sysfs doesn't add any of the
substates to the disable mask, enabling L1.1 actually enables *all* the
substates.

In this scenario:

  - Write 0 to "l1_aspm" to disable L1
  - Write 1 to "l1_1_aspm" to enable L1.1

the intention is to disable L1 and all L1.x substates, then enable just
L1.1, but in fact, *all* L1.x substates are enabled.

Fix this by explicitly disabling all the L1.x substates when disabling L1.

Fixes: 72ea91afbfb0 ("PCI/ASPM: Add sysfs attributes for controlling ASPM link states")
Link: https://lore.kernel.org/r/6ba7dd79-9cfe-4ed0-a002-d99cb842f361@gmail.com
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org