dino: remove unused dino_set_timer_irq() IRQ handler

dino: remove unused dino_set_timer_irq() IRQ handler

According to the comments in dino.c the timer IRQ is unused, so remove the empty
dino_set_timer_irq() handler function and simply pass NULL to mc146818_rtc_init()
in machine.c instead.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Acked-by: Helge Deller <deller@gmx.de>
Message-Id: <20220504092600.10048-19-mark.cave-ayland@ilande.co.uk>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>