kbuild: Allow drivers to fit src/drivers/[X]/[Y]/ scheme

Reorder drivers to fit src/drivers/[X]/[Y]/ scheme to make
them pluggable.

Also, fix up the following driver subdirectories by switching
to the src/drivers/[X]/[Y]/ scheme as these are hard requirements
for the main change:

* drivers/intel
* drivers/pc80
* drivers/dec

Change-Id: I455d3089a317181d5b99bf658df759ec728a5f6b
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/14047
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/Makefile.inc b/Makefile.inc
index 02ea674..0fb7a3d 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -75,7 +75,9 @@
 subdirs-y := src/lib src/commonlib/ src/console src/device src/acpi
 subdirs-y += src/ec/acpi $(wildcard src/ec/*/*) $(wildcard src/southbridge/*/*)
 subdirs-y += $(wildcard src/soc/*/*) $(wildcard src/northbridge/*/*)
-subdirs-y += src/superio $(wildcard src/drivers/*) src/cpu src/vendorcode
+subdirs-y += src/superio
+subdirs-y += $(wildcard src/drivers/*) $(wildcard src/drivers/*/*)
+subdirs-y += src/cpu src/vendorcode
 subdirs-y += util/cbfstool util/sconfig util/nvramtool util/broadcom
 subdirs-y += util/futility util/marvell
 subdirs-y += $(wildcard src/arch/*)