lib: sbi: fix sbi_domain_get_assigned_hartmask()

'1' is a 32 bit integer. When shifting it by more than 31 bits it becomes
zero and we get an incorrect return value.

Addresses-Coverity-ID: 1568356 Bad bit shift operation
Fixes: 296e70d6

 ("lib: sbi: Extend sbi_hartmask to support both hartid and hartindex")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>