fix(display): Fix epic_disp_rect() off-by-one regression

Make the new ctx based implementation behave just like the old one.
This means _including_ the yend row and xend column.

This fixes the G-Watch and DigiClk not looking as they should.

epicardium/drivers/display/api.c

@@ -251,7 +251,11 @@ int epic_disp_rect(
 	rgb565_to_rgb888(color, &r, &g, &b);
 
 	ctx_rectangle(
-		epicardium_ctx, xstart, ystart, xend - xstart, yend - ystart
+		epicardium_ctx,
+		xstart,
+		ystart,
+		xend - xstart + 1,
+		yend - ystart + 1
 	);
 
 	switch (fillstyle) {