load non opengles wallpapers for platforms without hardware graphics

Platforms without a hardware graphics, frequently get
"Unfortunately, System UI Crashed" pop-up message on boot-up, which
is due to an Android Runtime Exception
"java.lang.RuntimeException: eglConfig not initialized" when SystemUI
fail to load OpenGLES wallpapers.

This patch make sure that Android runtime checks for GPU availability
(by checking a build time property "ro.nohardwaregfx") before loading
opengles wallpapers.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>