soc/intel: Replace uses of dev_find_slot()

To call dev_find_slot(0, xx) in romstage can produce
invalid results since PCI bus enumeration has not
been progressed yet.

Replace this with method that relies on bus topology
that walks the root bus only.

Change-Id: I2883610059bb9fa860bba01179e7d5c58cae00e5
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33996
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/soc/intel/apollolake/memmap.c

@@ -35,7 +35,7 @@ void *cbmem_top(void)
 	if (!CONFIG(SOC_INTEL_GLK))
 		return tolum;
 
-	dev = dev_find_slot(0, PCH_DEVFN_LPC);
+	dev = pcidev_path_on_root(PCH_DEVFN_LPC);
 	assert(dev != NULL);
 	config = dev->chip_info;