CVE-2026-98935: rtc: dev: zero-initialize struct rtc_wkalrm to prevent information leak

In the Linux kernel, the following vulnerability has been resolved:

rtc: dev: zero-initialize struct rtcwkalrm to prevent information leak

The struct rtcwkalrm has padding holes after the 'pending' member. When returned to userspace via the RTCWKALRMRD ioctl, uninitialized kernel stack data residing in these holes may be leaked.

Zero-initialize the struct at declaration to eliminate this information leak risk.

Fixes smatch warnings: - drivers/rtc/dev.c:392 rtcdevioctl() warn: check that 'alarm' doesn't leak information (struct has a hole after 'pending')