scripts/mkits.sh: replace legacy backticks with $()

This replaces deprecated backticks by more versatile $(...) syntax.

Found with shellcheck.

Signed-off-by: Rosen Penev <[email protected]>
[adjust commit title and message]
Signed-off-by: Adrian Schmutzler <[email protected]>

scripts/mkits.sh

@@ -15,7 +15,7 @@
 #
 
 usage() {
-	echo "Usage: `basename $0` -A arch -C comp -a addr -e entry" \
+	echo "Usage: $(basename $0) -A arch -C comp -a addr -e entry" \
 		"-v version -k kernel [-D name -d dtb] -o its_file"
 	echo -e "\t-A ==> set architecture to 'arch'"
 	echo -e "\t-C ==> set compression type 'comp'"
@@ -55,7 +55,7 @@ if [ -z "${ARCH}" ] || [ -z "${COMPRESS}" ] || [ -z "${LOAD_ADDR}" ] || \
 	usage
 fi
 
-ARCH_UPPER=`echo $ARCH | tr '[:lower:]' '[:upper:]'`
+ARCH_UPPER=$(echo $ARCH | tr '[:lower:]' '[:upper:]')
 
 # Conditionally create fdt information
 if [ -n "${DTB}" ]; then