greybus: update svc_msg_header fields and users to match spec

The Greybus spec has been updated to clarify some of the original
intent of the SVC message definition. The svc_msg_header was:

struct svc_msg_header {
	__u8 function;
	__u8 message_type;
...
}

and is now

struct svc_msg_header {
	__u8 function_id;
	__u8 message_type;
...
}

to match the spec. The function_id carries enum svc_function_id values
and message_type is now clarified to be a session layer level field
that is simply "data" or "error".

Change all references of function type to function id. For now, don't
parse the message_type field but add the two allowable svc_msg_type enums.

Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
diff --git a/drivers/staging/greybus/svc_msg.h b/drivers/staging/greybus/svc_msg.h
index bbc7ef0..3f1a934 100644
--- a/drivers/staging/greybus/svc_msg.h
+++ b/drivers/staging/greybus/svc_msg.h
@@ -12,7 +12,7 @@
 
 #pragma pack(push, 1)
 
-enum svc_function_type {
+enum svc_function_id {
 	SVC_FUNCTION_HANDSHAKE			= 0x00,
 	SVC_FUNCTION_UNIPRO_NETWORK_MANAGEMENT	= 0x01,
 	SVC_FUNCTION_HOTPLUG			= 0x02,
@@ -22,9 +22,14 @@
 	SVC_FUNCTION_SUSPEND			= 0x06,
 };
 
+enum svc_msg_type {
+	SVC_MSG_DATA				= 0x00,
+	SVC_MSG_ERROR				= 0xff,
+};
+
 struct svc_msg_header {
-	__u8	function;
-	__u8	type;		/* enum svc_function_type */
+	__u8	function_id;	/* enum svc_function_id */
+	__u8	message_type;
 	__u8	version_major;
 	__u8	version_minor;
 	__le16	payload_length;