greybus: operation: Remove unused variable 'buffer'

'buffer' isn't used in this function, remove it.
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/operation.c

@@ -221,9 +221,7 @@ static void gb_operation_message_init(struct greybus_host_device *hd,
 				size_t payload_size, u8 type)
 {
 	struct gb_operation_msg_hdr *header;
-	u8 *buffer;
 
-	buffer = message->buffer;
 	header = message->buffer;
 
 	message->header = header;