symbols: add '_' to pci_drivers and cpu_drivers symbols

In order to prepare for more unification of the linker
scripts prefix pci_drivers, epci_drivers, cpu_drivers, and
ecpu_drivers with an underscore.

BUG=chrome-os-partner:44827
BRANCH=None
TEST=Built different boards includes ones w/ and w/o relocatable
     ramstage.

Change-Id: I8918b38db3b754332e8d8506b424f3c6b3e06af8
Signed-off-by: Aaron Durbin <adubin@chromium.org>
Reviewed-on: http://review.coreboot.org/11506
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/src/device/pci_device.c b/src/device/pci_device.c
index 6332209..f2e4d5d 100644
--- a/src/device/pci_device.c
+++ b/src/device/pci_device.c
@@ -850,7 +850,7 @@
 	 * Look through the list of setup drivers and find one for
 	 * this PCI device.
 	 */
-	for (driver = &pci_drivers[0]; driver != &epci_drivers[0]; driver++) {
+	for (driver = &_pci_drivers[0]; driver != &_epci_drivers[0]; driver++) {
 		if ((driver->vendor == dev->vendor) &&
 		    device_id_match(driver, dev->device)) {
 			dev->ops = (struct device_operations *)driver->ops;