drm/i915/ttm: fix 32b build

Since segment_pages is no longer a compile time constant, it looks the
DIV_ROUND_UP(node->size, segment_pages) breaks the 32b build. Simplest
is just to use the ULL variant, but really we should need not need more
than u32 for the page alignment (also we are limited by that due to the
sg->length type), so also make it all u32.

Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Fixes: bc99f120 ("drm/i915/ttm: fix sg_table construction")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Nirmoy Das <nirmoy.das@linux.intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220712174050.592550-1-matthew.auld@intel.com