Add support for enabling PCIe Common Clock and ASPM
These are guarded by individual Kconfig entries. The deprecated
CONFIG_PCIE_TUNING defines have been removed in favor of using specific
config options.
This is the generic half, there is board-specific pieces
still to come that tune before and after ASPM is enabled.
Change-Id: I3fe46282eada67629e9eeeed07e487dff54f2729
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: http://review.coreboot.org/735
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins)