platform: Allow platforms to specify the size of tlb fifo

For some platforms with a particularly high number of harts, if the
tlb fifo is too small, it case harts to wait. Platforms should be
allowed to specify the size of the tlb fifo.

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