net/mosquitto: depend on virtual package instead of select

Can't use DEPENDS:= +libname when libname is now a virtual package.
Switch to plain DEPENDS:= libname.

Fixes Github issue 4751

Signed-off-by: Karl Palsson <karlp@etactica.com>

net/mosquitto/Makefile

@@ -10,7 +10,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mosquitto
 PKG_VERSION:=1.4.14
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 PKG_LICENSE:=BSD-3-Clause
 PKG_LICENSE_FILES:=LICENSE.txt
 
@@ -144,7 +144,7 @@ endef
 define Package/libmosquittopp
     SECTION:=libs
     CATEGORY:=Libraries
-    DEPENDS:=+libmosquitto-ssl +libstdcpp
+    DEPENDS:=libmosquitto +libstdcpp
     TITLE:= mosquitto - client c++ library
 endef