rtc: renesas-rtca3: Disable interrupts only if the RTC is enabled

rtc: renesas-rtca3: Disable interrupts only if the RTC is enabled

If the RTC is not enabled and the code attempts to disable the interrupt,
the readb_poll_timeout_atomic() function in the
rtca3_alarm_irq_set_helper() may timeout, leading to probe failures.
This issue is reproducible on some devices because the initial values of
the PIE and AIE bits in the RCR1 register are undefined.

To prevent probe failures in this scenario, disable RTC interrupts only
when the RTC is actually enabled.

Fixes: d4488377609e ("rtc: renesas-rtca3: Add driver for RTCA-3 available on Renesas RZ/G3S SoC")
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://lore.kernel.org/r/20250205095519.2031742-1-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>