rtc: msc313: fix NULL deref in shared IRQ handler at probe

rtc: msc313: fix NULL deref in shared IRQ handler at probe

msc313_rtc_probe() calls devm_request_irq() with IRQF_SHARED and
&pdev->dev as the cookie, but platform_set_drvdata() is only called
later after the clock setup. With a shared IRQ line, another device
on the same line can trigger the handler in that window. The
handler does dev_get_drvdata() on the cookie, gets NULL, and
dereferences priv->rtc_base in interrupt context.

Pass priv as the cookie directly so the handler reads it from
dev_id without the lookup, removing the dependency on probe order.

Fixes: be7d9c9161b9 ("rtc: Add support for the MSTAR MSC313 RTC")
Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
Link: https://patch.msgid.link/20260511032703.48262-1-sozdayvek@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>