treewide: use only board_name function to get name

Do not parse /tmp/sysinfo/board_name, /proc/cpuinfo or the device tree
compatible string directly. Always use the board_name function to get
the board name.

The admswconfig package still reads /proc/cpuinfo directly. The code
looks somehow broken and the whole adm5120 which uses this package
looks unmaintained. Leave it as it is for now.

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

target/linux/mediatek/base-files/lib/upgrade/platform.sh

@@ -4,7 +4,7 @@
 
 platform_do_upgrade() {
 	local tar_file="$1"
-	local board="$(cat /tmp/sysinfo/board_name)"
+	local board="$(board_name)"
 
 	echo "flashing kernel"
 	tar xf $tar_file sysupgrade-$board/kernel -O | mtd write - kernel
@@ -17,7 +17,7 @@ platform_do_upgrade() {
 
 platform_check_image() {
 	local tar_file="$1"
-	local board=$(cat /tmp/sysinfo/board_name)
+	local board=$(board_name)
 
 	case "$board" in
 	mediatek,mt7623-rfb-nand-ephy |\
@@ -45,8 +45,7 @@ platform_check_image() {
 }
 
 platform_pre_upgrade() {
-	local board=$(cat /tmp/sysinfo/board_name)
-	case "$board" in
+	case "$(board_name)" in
 	mediatek,mt7623-rfb-nand-ephy |\
 	mediatek,mt7623-rfb-nand)
 		nand_do_upgrade $1