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>

src/Kconfig

@@ -432,6 +432,7 @@ source "src/superio/*/Kconfig"
 comment "Embedded Controllers"
 source "src/ec/acpi/Kconfig"
 source "src/ec/*/*/Kconfig"
+# FIXME move to vendorcode
 source "src/drivers/intel/fsp1_0/Kconfig"
 
 source "src/southbridge/intel/common/firmware/Kconfig"
@@ -445,6 +446,7 @@ source "src/device/Kconfig"
 
 menu "Generic Drivers"
 source "src/drivers/*/Kconfig"
+source "src/drivers/*/*/Kconfig"
 endmenu
 
 config RTC