lib: sbi: Fix shift bug in sbi_system_reset

There is a problem with judging whether the current hart belongs to
hmask. If cur_hartid minus hbase is greater than BITS_PER_LONG, the
previous hmask will also have a bit cleared incorrectly, which will
cause some harts to lose ipi.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>