anv: Round u_vector element sizes to a power of two

anv: Round u_vector element sizes to a power of two

This fixes 32-bit builds of the driver.  Commit 08413a81b93dc537fb0c3
changed things so that we now put struct anv_states in the u_vector for
binding tables.  On 64-bit builds, sizeof(struct anv_state) is a power
of two but it isn't on 32-bit builds.

Fixes: 08413a81b93dc537fb0c34327ad162f07e8c3427
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: mesa-stable@lists.freedesktop.org