zink: Fix BO size when it's not aligned to 16 bytes

glsl_get_explicit_size can return non-16 byte aligned sizes. Therefore, make sure the sure the size isrounded up so that OOB does not happen.

Fixes: ea8a0654 ("zink: further improve bo sizing") Reviewed-By: Mike Blumenkrantz michael.blumenkrantz@gmail.com Part-of: !17460 (merged)