treewide: drop target board_name functions

They are not used any longer.

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/ramips/base-files/lib/ramips.sh

@@ -716,12 +716,3 @@ ramips_board_detect() {
 	echo "$RAMIPS_BOARD_NAME" > /tmp/sysinfo/board_name
 	echo "$RAMIPS_MODEL" > /tmp/sysinfo/model
 }
-
-ramips_board_name() {
-	local name
-
-	[ -f /tmp/sysinfo/board_name ] && name=$(cat /tmp/sysinfo/board_name)
-	[ -z "$name" ] && name="unknown"
-
-	echo "${name}"
-}