etnaviv: Make sure rs alignment checks match

etnaviv: Make sure rs alignment checks match

etna_resource_alloc and etna_resource_from_handle currently use different checks.
This leads to

   etna_resource_from_handle:492: target=2, format=PIPE_FORMAT_B8G8R8X8_UNORM, 1080x1920x1, array_size=1, last_level=0, nr_samples=0, usage=0, bind=8000a, flags=0
   etna_resource_from_handle:541: BO stride 4320 is too small for RS engine width padding (4352, format PIPE_FORMAT_B8G8R8X8_UNORM)

since etna_resource_from_handle wants to be aligned to a 16 byte
boundary while the etna_resource_alloc does not.

Adjust the two checks by using a common function.

Broken by baff59ebf07a114f95ad66d1f54e4b1f409eebee

Signed-off-by: Guido Günther <guido.gunther@puri.sm>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>