forked from Mirrors/opensbi

The P2A doorbell system MSI index is expected to be discovered from device tree instead of RPMI system MSI service group attribute. This is based on ARC feedback before RPMI spec was frozen. Let's parse P2A doorbell system MSI index from device tree and also expose it as rpmi channel attribute to RPMI client drivers. Signed-off-by: Anup Patel <apatel@ventanamicro.com> Link: https://lore.kernel.org/r/20250512083827.804151-3-apatel@ventanamicro.com Signed-off-by: Anup Patel <anup@brainfault.org>