drm/i915: Switch intel_usecs_to_scanlines() to 64bit maths

Dotclocks can reach ~1GHz these days, so intel_usecs_to_scanlines(),
with its 32bit maths, is currently limited to a few milliseconds.
I want bigger numbers in DSB selftests, so switch over to 64bit
maths.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240528185647.7765-7-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_crtc.c

@@ -454,7 +454,7 @@ int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
 	if (!adjusted_mode->crtc_htotal)
 		return 1;
 
-	return DIV_ROUND_UP(usecs * adjusted_mode->crtc_clock,
+	return DIV_ROUND_UP_ULL(mul_u32_u32(usecs, adjusted_mode->crtc_clock),
 				1000 * adjusted_mode->crtc_htotal);
 }