auxdisplay: hd44780_common: Reduce clear_display timeout

Digging in the hd44780 datasheet revealed that the timeout needed after
clearing the whole display is only 1,64ms not 15ms. So we can reduce
that timeout.

Link: https://lore.kernel.org/lkml/20200922092121.GG16421@1wt.eu/
Link: https://www.crystalfontz.com/controllers/Hitachi/HD44780/433/Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

drivers/auxdisplay/hd44780_common.c

@@ -83,8 +83,8 @@ int hd44780_common_clear_display(struct charlcd *lcd)
 	struct hd44780_common *hdc = lcd->drvdata;
 
 	hdc->write_cmd(hdc, LCD_CMD_DISPLAY_CLEAR);
-	/* we must wait a few milliseconds (15) */
-	long_sleep(15);
+	/* datasheet says to wait 1,64 milliseconds */
+	long_sleep(2);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(hd44780_common_clear_display);