lib: Simplify the for-loop in sbi_ipi_send_many()

We don't need to separately call sbi_ipi_send() for current HART
in sbi_ipi_send_many(). Instead, we can simplify the for-loop in
sbi_ipi_send_many() and call sbi_ipi_send() for all HARTs in the
for-loop itself.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>