kernel: time: Fix the alarm_bases array accessing issue

Array 'alarm_bases' of size 2 may use index value(s) 0..2,
so check the alarm type before initializing.

CRs-fixed: 2206448
Change-Id: I4691b5a8a92c8a98dc78c8938a0dc9c0852c4e2e
Signed-off-by: Vamshi Krishna B V <vbv@codeaurora.org>