PCI ASPM: do not clear enabled field by support field

We must not clear bits in 'aspm_enabled' using 'aspm_support', or
'aspm_enabled' and 'aspm_default' might be different from the actual
state. In addtion, 'aspm_default' should be intialized even if
'aspm_support' is 0.

Acked-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>