Revert "kernel-devicetree: Corrected normalize_dtb"

This reverts commit 2e7f3b2b9318d1e5395ad58131eafb873f614326.

It was breaking quite common use case that the dtb files are in
some subdirectory and then kernel build fails to build them.

As reported by khem:
http://lists.openembedded.org/pipermail/openembedded-core/2018-July/152578.html
me:
http://lists.openembedded.org/pipermail/openembedded-core/2018-July/152579.html
on raspberrypi3 build:

make[3]: *** No rule to make target 'arch/arm/boot/dts/dwc2.dtbo'.  Stop.
arch/arm/Makefile:345: recipe for target 'dwc2.dtbo' failed
make[2]: *** [dwc2.dtbo] Error 2
Makefile:146: recipe for target 'sub-make' failed

and trevor on the IRC:
20:35:49 < tlwoerner> the recent 2e7f3b2b9318d1e5395ad58131eafb873f614326 commit in oe-core seems to cause dragonboard-410c's kernel to fail to build
20:36:26 < tlwoerner> for the dragonboard-410c, KERNEL_DEVICETREE is set to "qcom/apq8016-sbc.dtb" but the build failure is:
20:36:37 < tlwoerner> *** No rule to make target 'arch/arm64/boot/dts/dts/qcom/apq8016-sbc.dtb'.  Stop.
20:36:44 < tlwoerner> i.e. the "qcom/" is getting removed
20:37:08 < tlwoerner> oops!!
20:37:33 < tlwoerner> wrong copy&paste, the actual error is:
20:37:36 < tlwoerner> *** No rule to make target 'arch/arm64/boot/dts/apq8016-sbc.dtb'.  Stop.
20:37:53 < tlwoerner> i.e., the "qcom/" is being stripped out

(From OE-Core rev: 0d725c76c113dec441a7319a6ee997e4ae8c4c88)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/kernel-devicetree.bbclass

@@ -13,8 +13,8 @@ normalize_dtb () {
 	DTB="$1"
 	if echo ${DTB} | grep -q '/dts/'; then
 		bbwarn "${DTB} contains the full path to the the dts file, but only the dtb name should be used."
+		DTB=`basename ${DTB} | sed 's,\.dts$,.dtb,g'`
 	fi
-	DTB=`basename ${DTB} | sed 's,\.dts$,.dtb,g'`
 	echo "${DTB}"
 }