drivers/arm/scmi: allow use of multiple SCMI channels

On systems that have multiple platform components that can interpret the
SCMI messages, there is a need to support multiple SCMI channels (one
each to those platform components). Extend the existing SCMI interface
that currently supports only a single SCMI channel to support multiple
SCMI channels.

Change-Id: Ice4062475b903aef3b5e5bc37df364c9778a62c5
Signed-off-by: Aditya Angadi <aditya.angadi@arm.com>
diff --git a/plat/arm/css/sgi/sgi_bl31_setup.c b/plat/arm/css/sgi/sgi_bl31_setup.c
index 2ff66ac..3d2d933 100644
--- a/plat/arm/css/sgi/sgi_bl31_setup.c
+++ b/plat/arm/css/sgi/sgi_bl31_setup.c
@@ -36,7 +36,7 @@
 		.ring_doorbell = &mhuv2_ring_doorbell,
 };
 
-scmi_channel_plat_info_t *plat_css_get_scmi_info(void)
+scmi_channel_plat_info_t *plat_css_get_scmi_info(int channel_id)
 {
 	if (sgi_plat_info.platform_id == RD_N1E1_EDGE_SID_VER_PART_NUM)
 		return &rd_n1e1_edge_scmi_plat_info;