dm: SMEM (Shared memory) uclass

This is a uclass for Shared memory manager drivers.

A Shared Memory Manager driver implements an interface for allocating
and accessing items in the memory area shared among all of the
processors.

Signed-off-by: Ramon Fried <ramon.fried@gmail.com>

Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

include/dm/uclass-id.h

@@ -74,6 +74,7 @@ enum uclass_id {
 	UCLASS_RTC,		/* Real time clock device */
 	UCLASS_SCSI,		/* SCSI device */
 	UCLASS_SERIAL,		/* Serial UART */
+	UCLASS_SMEM,		/* Shared memory interface */
 	UCLASS_SPI,		/* SPI bus */
 	UCLASS_SPMI,		/* System Power Management Interface bus */
 	UCLASS_SPI_FLASH,	/* SPI flash */