libvirtual: Fix logic to detect DRC use case.

We detect DRC based on the resolution of the external display stored
in the HAL, and the dimensions of the framebuffer(fb2) after receiving
a RESUME event. If the stored resolution is greater than that of fb2
it means fb2 was reconfigured due to DRC. This is the only case in
which we trigger the DRC path (and the MDP downscale path thereafter).

For all other cases, the RESUME event is just treated as normal and
should not result in triggering the DRC path.

Change-Id: I2c8a854434f09a840938f00b88faa59c6cb57e7f