lib: Prepare for libhwbase' generated config file

Add new libhwbase options and add a class for files generated during
build. This follows the same pattern as for libgfxinit.

Change-Id: Ie5b84992fa687e4e94b6d959a64086c638f66eb8
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/20626
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/lib/Kconfig

@@ -22,4 +22,11 @@ if RAMSTAGE_LIBHWBASE
 config HWBASE_DYNAMIC_MMIO
 	def_bool y
 
+config HWBASE_DEFAULT_MMCONF
+	hex
+	default MMCONF_BASE_ADDRESS
+
+config HWBASE_DIRECT_PCIDEV
+	def_bool y
+
 endif