i965: Force VMA alignment to be a multiple of the page size.

This should happen regardless, but let's be paranoid.

Fixes: 01058a5522 i965: Add virtual memory allocator infrastructure to brw_bufmgr.
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/mesa/drivers/dri/i965/brw_bufmgr.c

@@ -402,6 +402,8 @@ vma_alloc(struct brw_bufmgr *bufmgr,
    /* Without softpin support, we let the kernel assign addresses. */
    assert(brw_using_softpin(bufmgr));
 
+   alignment = ALIGN(alignment, PAGE_SIZE);
+
    struct bo_cache_bucket *bucket = get_bucket_allocator(bufmgr, size);
    uint64_t addr;