build/clean/u-boot: improved coding style

tabs for indentation

simplify some checks

resources/scripts/build/clean/u-boot

@@ -33,17 +33,14 @@ printf "Cleaning u-boot builds for all boards\n"
 
 # clean u-boot (source archives preserved)
 for board in u-boot/*; do
-    if [ "${board##*/}" = "u-boot" ]; then
-        continue
-    fi
-    if [ ! -d "${board}" ]; then
+	if [ "${board##*/}" = "u-boot" ] || [ ! -d "${board}" ]; then
 		continue
 	fi
+
 	make -C "${board}/" distclean
 
-    if [ -e "${board}/.git" ]; then
+	[ -e "${board}/.git" ] && \
 		git -C "${board}" clean -fdx
-    fi
 done
 
 printf "\n\n"