kbuild: automatically include ECs

This change switches all ECs and the generic EC ACPI code
to be autoincluded by Makefile.inc, rather than having to be
mentioned explicitly in ec/Makefile.inc or in
ec/<vendor>/Makefile.inc.

This means, vendor and ec directories are now "drop
in", e.g. be placed in the coreboot directory hierarchy
without having to modify any higher level coreboot files.

The long term plan is to enable out of tree components to be
built with a given coreboot version (given that the API did not
change).

Change-Id: I29d757d1f8c10a1d0167a76fd0d0f97bac576f6d
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: http://review.coreboot.org/9798
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/Makefile.inc b/Makefile.inc
index c1e7def..628fbdf 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -52,7 +52,9 @@
 
 #######################################################################
 # root source directories of coreboot
-subdirs-y := src/lib src/console src/device src/ec $(wildcard src/southbridge/*/*) src/soc
+subdirs-y := src/lib src/console src/device
+subdirs-y += src/ec/acpi $(wildcard src/ec/*/*) $(wildcard src/southbridge/*/*)
+subdirs-y += src/soc
 subdirs-y += src/northbridge src/superio src/drivers src/cpu src/vendorcode
 subdirs-y += util/cbfstool util/sconfig util/nvramtool util/broadcom
 subdirs-y += $(wildcard src/arch/*)