rtc: class: Remove duplicate check for alarm

In __devm_rtc_register_device(), the callee rtc_initialize_alarm()
will check the alarm, there is no need to check in advance,
so remove it.

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Link: https://patch.msgid.link/20260122090031.3871746-1-ruanjinjie@huawei.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>