drivers: Add SPMI bus uclass

Qualcom processors use proprietary bus to talk with PMIC devices -
SPMI (System Power Management Interface).
On wiring level it is similar to I2C, but on protocol level, it's
multi-master and has simple autodetection capabilities.
This commit adds simple uclass that provides bus read/write interface.

Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 37c4176..cbf9b2c 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -66,6 +66,7 @@
 	UCLASS_RTC,		/* Real time clock device */
 	UCLASS_SERIAL,		/* Serial UART */
 	UCLASS_SPI,		/* SPI bus */
+	UCLASS_SPMI,		/* System Power Management Interface bus */
 	UCLASS_SPI_FLASH,	/* SPI flash */
 	UCLASS_SPI_GENERIC,	/* Generic SPI flash target */
 	UCLASS_SYSCON,		/* System configuration device */