iris: correctly set alignment to next power of two for struct size

iris: correctly set alignment to next power of two for struct size

We're currently aligning the offset to the size of the data structure
itself when the upload manager actually expects a POT. Ideally this
would be the next POT that's greater than the size of the structure.

Fixes: c24a574e6c78 ("iris: Don't allocate a BO per query object")

Signed-off-by: Rohan Garg <rohan.garg@intel.com>
Reviewed-by: Sagar Ghuge <sagar.ghuge@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20153>