soc: qcom: smem: add build infra

Build the new SMEM driver port, and select it when ARCH_SNAPDRAGON is
selected, since it will be a hard dependency for Qualcomm platforms.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/soc/qcom/Kconfig

@@ -24,4 +24,12 @@ config QCOM_RPMH
 	  Say y here to support the Qualcomm RPMh (resource peripheral manager)
 	  if you need to control regulators on Qualcomm platforms, say y here.
 
+config QCOM_SMEM
+	bool "Qualcomm SMEM support"
+	help
+	  Say y here to support the Qualcomm SMEM (shared memory) client driver.
+	  SMEM is a shared memory region that is used to pass information about
+	  the hardware (e.g. DRAM layout, PMIC configuration, etc) between bootloader
+	  staged and the OS. If in doubt, say y.
+
 endif # SOC_QCOM

drivers/soc/qcom/Makefile

@@ -2,3 +2,4 @@
 
 obj-$(CONFIG_QCOM_COMMAND_DB) += cmd-db.o
 obj-$(CONFIG_QCOM_RPMH) += rpmh-rsc.o rpmh.o
+obj-$(CONFIG_QCOM_SMEM) += smem.o