baytrail: pcie: Root port initialization

Add PCIe driver to initialize root ports.

BUG=chrome-os-partner:24111
TEST=Manual on Rambi. Verify that PCIe Wifi card is detected and able to
detect networks.
BRANCH=None.

Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>

Change-Id: I3c68da5f27cd162e112add488bdf5ced192b7d12
Reviewed-on: https://chromium-review.googlesource.com/177652
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Commit-Queue: Shawn Nematbakhsh <shawnn@chromium.org>
Tested-by: Shawn Nematbakhsh <shawnn@chromium.org>
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/4981
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/soc/intel/baytrail/chip.h

@@ -29,6 +29,7 @@ struct soc_intel_baytrail_config {
         uint8_t sata_port_map;
         uint8_t sata_ahci;
         uint8_t ide_legacy_combined;
+	uint8_t clkreq_enable;
 
 	/* USB Port Disable mask */
 	uint16_t usb2_port_disable_mask;