debug-snapshot-log: Reduce IRQ info

In order to print less log to make room for other logs.
Uses IRQ_THRESHOLD * boot time to filter normal IRQ. Since no IRQ
should reach 50 times per second beside system IRQ. Set IRQ_THRESHOLD
to 50.

Bug: 332426051
Test: echo c > /proc/sysrq-trigger and check irq info
Change-Id: I838aa119ae214f533c83ee64fffd1642bf6b64ce
Signed-off-by: Eric Lai <ericllai@google.com>