scripts/dtc: dt_to_config - kernel config options for a devicetree

Determining which kernel config options need to be enabled for a
given devicetree can be a painful process.  Create a new tool to
find the drivers that may match a devicetree node compatible,
find the kernel config options that enable the driver, and
optionally report whether the kernel config option is enabled.

Signed-off-by: Gaurav Minocha <gaurav.minocha.os@gmail.com>
Signed-off-by: Frank Rowand <frank.rowand@am.sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>

scripts/dtc/dtx_diff

@@ -266,7 +266,7 @@ DTC="${__KBUILD_OUTPUT}/scripts/dtc/dtc"
 
 if [ ! -x ${DTC} ] ; then
 	__DTC="dtc"
-	if grep -q "^CONFIG_DTC=y" ${__KBUILD_OUTPUT}/.config ; then
+	if grep -q "^CONFIG_DTC=y" ${__KBUILD_OUTPUT}/.config 2>/dev/null; then
 		make_command='
          make scripts'
 	else