mvebu: replace backticks by $(...)

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

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
[decapitalized patch subject at submitter's request]
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

target/linux/mvebu/base-files/lib/upgrade/linksys.sh

@@ -6,7 +6,7 @@ linksys_get_target_firmware() {
 
 	local cur_boot_part mtd_ubi0
 
-	cur_boot_part=`/usr/sbin/fw_printenv -n boot_part`
+	cur_boot_part=$(/usr/sbin/fw_printenv -n boot_part)
 	if [ -z "${cur_boot_part}" ] ; then
 		mtd_ubi0=$(cat /sys/devices/virtual/ubi/ubi0/mtd_num)
 		case $(egrep ^mtd${mtd_ubi0}: /proc/mtd | cut -d '"' -f 2) in

target/linux/mvebu/base-files/sbin/fan_ctrl.sh

@@ -1,8 +1,8 @@
 #!/bin/sh
 
-CPU_TEMP=`cut -c1-2 /sys/class/hwmon/hwmon2/temp1_input`
-DDR_TEMP=`cut -c1-2 /sys/class/hwmon/hwmon1/temp1_input`
-WIFI_TEMP=`cut -c1-2 /sys/class/hwmon/hwmon1/temp2_input`
+CPU_TEMP=$(cut -c1-2 /sys/class/hwmon/hwmon2/temp1_input)
+DDR_TEMP=$(cut -c1-2 /sys/class/hwmon/hwmon1/temp1_input)
+WIFI_TEMP=$(cut -c1-2 /sys/class/hwmon/hwmon1/temp2_input)
 
 CPU_LOW=85
 CPU_HIGH=95