Support yocto builds

Yocto module class uses KERNEL_SRC instead of the widespread KDIR. Make
sure we honor that variable too.

Remove now redundant Kbuild include, and simplify rules while at it.

Signed-off-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>

Author: bemug-st

Jenkinsfile

@@ -33,7 +33,7 @@ pipeline {
 		stage('Build') {
 			steps {
 				dir('pristine') {
-					sh 'make KVERSION=$(ls /lib/modules/)'
+					sh 'make KDIR=/lib/modules/$(ls /lib/modules/)/build'
 				}
 			}
 		}

Kbuild

@@ -1 +1 @@
-obj-$(CONFIG_DRIVER_VD1943)     += vd1943.o
+obj-m += vd1943.o

Makefile

@@ -1,13 +1,12 @@
-ifneq ($(KERNELRELEASE),)
-include Kbuild
+KDIR ?= /lib/modules/`uname -r`/build
+KERNEL_SRC ?= $(KDIR)
+SRC := $(shell pwd)
 
-else
-KVERSION ?= `uname -r`
-KDIR ?= /lib/modules/${KVERSION}/build
-default:
-	CONFIG_DRIVER_VD1943=m $(MAKE) -C $(KDIR) M=$$PWD
+all:
+	$(MAKE) -C $(KERNEL_SRC) M=$(SRC)
 
-clean:
-	CONFIG_DRIVER_VD1943=m $(MAKE) -C $(KDIR) M=$$PWD clean
+modules_install:
+	$(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install
 
-endif
+clean:
+	$(MAKE) -C $(KERNEL_SRC) M=$(SRC) clean