platform: Uses hart count as the default size of tlb info

For platform with high number of harts, it is better to auto detect a
suitable number of entries in tlb fifo. Since allocating tlb entry for
all online harts can reduce the wait time significantly, using the
number of the online harts can make most platforms happy. This auto
detection can avoid most duplicate code for setting tlb fifo size.

Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
Acked-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>