compile_pkgs: git option is depth not deep

Thanks to midnightmagic, who pointed out it on IRC channel #turris on Freenode

compile_pkgs

@@ -269,7 +269,7 @@ checkout() {
 		git fetch origin
 		git checkout -f "$githash"
 	else
-		git fetch ${CLONE_DEEP+--deep 1} origin "$OPENWRT_BRANCH"
+		git fetch ${CLONE_DEEP+--depth 1} origin "$OPENWRT_BRANCH"
 		git checkout -f "origin/$OPENWRT_BRANCH"
 	fi
 	_checkout_clean