We don't want tile 0,0 to artificially constrain the size of the legacy
fbdev device.  Instead when reducing fb_size to be the minimum of all
displays, only consider the rightmost and bottommost tiles.
Signed-off-by: NRob Clark <robdclark@gmail.com>
Tested-by: NHai Li <hali@codeaurora.org>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>