swr/rasterizer: Use private functions for min/max to avoid namespace issues.

swr/rasterizer: Use private functions for min/max to avoid namespace issues.

This is a similiar fix as bb2287ccdf46 ("gallivm/tessellator: use
private functions for min/max to avoid namespace issues").

Fixes: ab5570820071 ("swr/rasterizer: Add tessellator implementation to the rasterizer")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Jan Zielinski <jan.zielinski@intel.com>
Tested-by: Jan Zielinski <jan.zielinski@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4208>