mach-snapdragon: implement capsule update support

Qualcomm boards flash U-Boot a variety of partitions, implement support
for determining which slot U-Boot is running from, finding the correct
partition for that slot and configuring the appropriate DFU string.

Initially, we only support the RB3 Gen 2 where U-Boot is flashed to the
UEFI partition, and ignore handling of slots. In the future we will
additionally support booting U-Boot from other partitions (e.g. boot)
and correct handling for A/B.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
diff --git a/arch/arm/mach-snapdragon/qcom-priv.h b/arch/arm/mach-snapdragon/qcom-priv.h
index 0a7ed5e..74d3919 100644
--- a/arch/arm/mach-snapdragon/qcom-priv.h
+++ b/arch/arm/mach-snapdragon/qcom-priv.h
@@ -3,6 +3,12 @@
 #ifndef __QCOM_PRIV_H__
 #define __QCOM_PRIV_H__
 
+#if IS_ENABLED(CONFIG_EFI_HAVE_CAPSULE_SUPPORT)
+void qcom_configure_capsule_updates(void);
+#else
+void qcom_configure_capsule_updates(void) {}
+#endif /* EFI_HAVE_CAPSULE_SUPPORT */
+
 #if CONFIG_IS_ENABLED(OF_LIVE)
 /**
  * qcom_of_fixup_nodes() - Fixup Qualcomm DT nodes