Patch merged into coreboot/master: PCIEXP_PLUGIN_SUPPORT: Change dependency on PCI access

the following patch was just integrated into master:
commit 91bfa8e7eaf7a91c47a3e86c35ffe2135aa0cd8f
Author: Kyösti Mälkki 
Date:   Sun Nov 20 20:39:56 2016 +0200

PCIEXP_PLUGIN_SUPPORT: Change dependency on PCI access

Some PCI-e capability registers are located starting from
    0x100, these are not accessible using the conventional
    PCI IO config operations at 0xcf8/0xcfc, unless PCI_CFG_EXT_IO
    was selected.

Thus any feature that calls pciexp_find_extended_cap()
    depends on either MMCONF_SUPPORT_DEFAULT or PCI_CFG_EXT_IO
    being enabled on the platform.

In theory there can be system without MMCONF_SUPPORT, but
    with complete PCI Express configuration space available
    using PCI_CFG_EXT_IO. Do not use explicit PCI MMCONF
    operations here, but rely on the default PCI access
    method to be able to access all of the configuration space.

While at it, convert to IS_ENABLED() everywhere in the source
    and organize Kconfig file better.

Change-Id: Ica6e16d2fb2adc532e644c4b2c47806490235715
    Signed-off-by: Kyösti Mälkki 
    Reviewed-on: https://review.coreboot.org/17546
    Tested-by: build bot (Jenkins)
    Reviewed-by: Aaron Durbin

See https://review.coreboot.org/17546 for details.

-gerrit