phosphor-watchdog: Enable sdeventplus support

An upcoming commit to phosphor-watchdog will require sdeventplus during
the build process.

Tested:
    Build still works as expected. Manually patching in the sdeventplus
    patch works as expected.

Change-Id: If7ec7a667a505144659351a919c009bb9d3d8113
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/recipes-phosphor/watchdog/phosphor-watchdog.bb b/recipes-phosphor/watchdog/phosphor-watchdog.bb
index 55a7447..0ab2be9 100644
--- a/recipes-phosphor/watchdog/phosphor-watchdog.bb
+++ b/recipes-phosphor/watchdog/phosphor-watchdog.bb
@@ -13,6 +13,7 @@
 
 DEPENDS += "autoconf-archive-native"
 DEPENDS += "sdbusplus sdbusplus-native"
+DEPENDS += "sdeventplus"
 DEPENDS += "phosphor-dbus-interfaces"
 DEPENDS += "phosphor-logging"
 RDEPENDS_${PN} += "libsystemd"