PCI ASPM: support L1 only

PCI ASPM: support L1 only

The definition of the ASPM support field in the Link Capabilities
Register had been changed by the "ASPM optionality ECN" as follows:

<Before>
	00b	Reserved
	01b	L0s Supported
	10b	Reserved
	11b	L0s and L1 Supported

<After>
	00b	No ASPM Support
	01b	L0s Supported
	10b	L1 Supported
	11b	L0s and L1 Supported

Current linux ASPM driver doesn't enable ASPM if the support field is
00b or 10b. So there is no impact about 00b. But current linux ASPM
driver doesn't enable L1 if the support field is 10b. With this patch,
10b (L1 support) is handled properly.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>