util: Use sizeof(void *) rather than 0 as the fallback cache line size

util: Use sizeof(void *) rather than 0 as the fallback cache line size

Without this, llvmpipe ends up giving a zero size to all uncompressed textures
on non-x86 systems, since align() cannot handle a 0 alignment.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Richard Sandiford <rsandifo@linux.vnet.ibm.com>