lib: utils/irqchip: Check before initializing imsic

The current mlevel imsic check is only for the platform, which
may cause hart without imsic in the platform to trigger an
illegal instruction exception when initializing imsic. For
example, the platform contains a management hart that only
supports wired interrupts.

This patch will check if each hart supports Smaia extension
before doing imsic initialization to avoid triggering illegal
instruction exceptions.

Signed-off-by: Cheng Yang <yangcheng.work@foxmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>