Do not build eglfs QPA when cross compiling for QNX

Commit 2a1b50d67c introduced a dependency
on evdev for eglfs which QNX does not provide. QNX also has a dedicated
QPA plugin so the eglfs plugin is not needed there.

It is not possible to use the -device configure defaults approach as
it is not cross-platform.

Change-Id: I2d151f16cf1a9576a0b0b528f0e9c17834c66e91
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>

configure

@@ -4742,7 +4742,7 @@ elif [ "$CFG_OPENGL" = "desktop" ]; then
 fi
 
 if [ "$CFG_EGLFS" != "no" ]; then
-    if [ "$CFG_OPENGL" = "es2" ]; then
+    if [ "$CFG_OPENGL" = "es2" ] && [ "$XPLATFORM_QNX" = "no" ]; then
         CFG_EGLFS="$CFG_EGL"
     else
         CFG_EGLFS="no"