etnaviv: optimize RS transfers

etnaviv: optimize RS transfers

Currently we are blitting the whole resource when the RS is used to
de-/tile a resource. This can be very inefficient for large resources
where the transfer is only changing a small part of the resource
(happens a lot with glTexSubImage2D).

Optimize this by only blitting the tile aligned subregion of the
resource, which the transfer is going to change.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-By: Wladimir J. van der Laan <laanwj@gmail.com>