DisplayDevice: Backwards compatibility with old EGL

From 4.1 to 4.2, the display subsystem was reworked to
use SurfaceTextureClient/BufferQueue instead of
FramebufferNativeWindow for the framebuffer itself.

Unfortunately, some legacy EGL libraries make assumptions
that any framebuffer device will be FramebufferNativeWindow.

These EGL libraries will fail when used in 4.2 as if the
framebuffer is not FramebufferNativeWindow, they will
try to dequeue more than one buffer at a time, which
will cause a hang of the graphics subsystem.

This allows use of FramebufferNativeWindow to keep
legacy EGL implementations happy.  Confirmed EGL
implementations that need this include but are
not limited to:

Set BOARD_EGL_NEEDS_FNW to use

Tegra2/3 ICS EGL
Mali400 ICS EGL (Allwinner A10)
Mali400 Jellybean (4.1) EGL (Samsung Exynos4)
Adreno Jellybean (4.1) EGL (legacy qcom devices using PMEM)