dectmngr-init: add few arguments for dectmngr

Add few arguments for dectmngr, which is based on the UCI config for
asterisk and dect:

    -sync $pcm_fsync (UCI dect.global.pcm_fsync)

    -slotsShift $pcm_slot_start (UCI dect.global.pcm_slot_star)

    -extensionShift N (starting index of UCI asterisk.extensionN for DECT)

dectmngr/files/etc/init.d/dectmngr

@@ -11,6 +11,25 @@ LOG_PATH=/var/log/dectmngr
 DB_PATH=/etc/dect
 DCX81_UART_DT_ALIAS=/proc/device-tree/aliases/dcx81-uart
 
+get_extension_shift() {
+   local dect_exts
+
+   get_dect_extension() {
+       local ext=$1
+       local type
+
+       config_get type $ext type
+
+       [ "$type" == "dect" ] && echo $ext
+    }
+
+    config_load "asterisk"
+
+    dect_exts=$(config_foreach get_dect_extension "extension" |sort |head -n1)
+
+    echo "${dect_exts#extension}"
+}
+
 # Ask dectmngr to exit nicely and wait for it to clean up, which is a slow process.
 stop_and_wait_dectmngr() {
 	dect_pid=$(pidof $PROG)
@@ -56,6 +75,8 @@ start_service() {
 		return 0
 	fi
 
+	opt_ext="-extensionShift $(get_extension_shift)"
+
 	local dcx81_uart_device
 	if ! dcx81_uart_device="$(get_dcx81_device)"; then
 		logger -t "$PROG" -p daemon.warning "Could not determine DCX81 UART device. Falling back to default ttyH0."
@@ -77,6 +98,11 @@ start_service() {
 
 	config_load dect
 	config_get log_dect_cmbs global log_dect_cmbs syslog
+	config_get pcm_slot_start global pcm_slot_start
+	config_get pcm_fsync global pcm_fsync
+
+        [ -n "$pcm_fsync" ] && opt_ext="$opt_ext -sync $pcm_fsync"
+        [ -n "$pcm_slot_start" ] && opt_ext="$opt_ext -slotsShift $pcm_slot_start"
 
 	procd_open_instance