forked from Mirrors/opensbi

The generic platform provides IPI and timer functionality based on DT node provided in the FDT passed by previous booting stage. This patch updates generic platform documentation about IPI and timer expectations. Signed-off-by: Anup Patel <anup.patel@wdc.com> Reviewed-by: Bin Meng <bin.meng@windriver.com> Reviewed-by: Atish Patra <atish.patra@wdc.com>