eglfs: Support for alternative Mali driver packages

In addition to the proprietary Mali Linux driver bundle from ARM, there
are a couple of semi open source alternative bundles out in the wild,
which are mostly derivatives from the sunxi-mali bundle.

The non-ARM bundles lacks the proprietary header file fbdev_window.h
which defines the fbdev_window struct. Instead, it has an equivalent
mali_native_window struct in the EGL/eglplatform.h (which in turn is
included by EGL/egl.h).

This change adds an alternative configure test which detects the non-ARM
bundles are used. It also removes the dependency on fbdev_window.h by
defining the structure ourselves, which actually makes the plugin
potentially compilable with *any* EGL SDK.

Change-Id: I78ab4b618e8e9c774c889fe9896105cf2cf4228e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>