package/mpd: add libmodplug optional dependency

libmodplug is an optional dependency since version 0.15.0 and
https://github.com/MusicPlayerDaemon/MPD/commit/d838a1ad24a9eaac44367e34506373b4b71e4ff0

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/mpd/Config.in

@@ -140,6 +140,12 @@ config BR2_PACKAGE_MPD_MAD
 	  Enable mad input support.
 	  Select this if you want to play back MP3 files.
 
+config BR2_PACKAGE_MPD_MODPLUG
+	bool "modplug"
+	select BR2_PACKAGE_LIBMODPLUG
+	help
+	  Enable Modplug decoder support.
+
 config BR2_PACKAGE_MPD_MPG123
 	bool "mpg123"
 	select BR2_PACKAGE_LIBID3TAG

package/mpd/mpd.mk

@@ -180,6 +180,13 @@ else
 MPD_CONF_OPTS += -Dmad=disabled
 endif
 
+ifeq ($(BR2_PACKAGE_MPD_MODPLUG),y)
+MPD_DEPENDENCIES += libmodplug
+MPD_CONF_OPTS += -Dmodplug=enabled
+else
+MPD_CONF_OPTS += -Dmodplug=disabled
+endif
+
 ifeq ($(BR2_PACKAGE_MPD_MPG123),y)
 MPD_DEPENDENCIES += libid3tag mpg123
 MPD_CONF_OPTS += -Dmpg123=enabled