dt-bindings: rtc: brcm,brcmstb-waketimer: add alarm interrupt

A second interrupt can optionally be specified for this device
to be used for generating RTC alarm interrupts.

Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230124201430.2502371-2-opendmb@gmail.com


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