drm/vmwgfx: limit mode size for all display unit to texture_max

For all display units, limit mode size exposed to texture_max_width/
height as this is the maximum framebuffer size that virtual device can
create.

Signed-off-by: Deepak Rawat <drawat@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>