rtc: amlogic-a4: fix compile error

When compile rtc-a4, build error as following:
ERROR: modpost: drivers/rtc/rtc-amlogic-a4: struct of_device_id is
not terminated with a NULL entry!
This commit is to fix it.

Fixes: c89ac918 ("rtc: support for the Amlogic on-chip RTC")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Link: https://lore.kernel.org/r/20241113-fix_a4_rtc-v1-1-307af26449a8@amlogic.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>