drm/i915/display: Don't use "proxy" headers

The driver uses math.h and not util_macros.h.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231129140129.699767-1-andriy.shevchenko@linux.intel.com