feat(fwu): add a function to pass metadata structure to platforms

Add a helper function to pass the metadata structure to the
platforms. Platforms can then read the metadata structure and pass the
boot index value, i.e. the bank(partition) from which the firmware
images were booted, to the Update Agent.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Change-Id: I571179b9baa0fbc4d0f08d7a6e3b50c0c7165c5c

drivers/fwu/fwu.c

@@ -157,6 +157,13 @@ bool fwu_is_trial_run_state(void)
 	return trial_run;
 }
 
+const struct fwu_metadata *fwu_get_metadata(void)
+{
+	assert(is_fwu_initialized);
+
+	return &metadata;
+}
+
 /*******************************************************************************
  * Load verified copy of FWU metadata image kept in the platform NV storage
  * into local FWU metadata structure.

include/drivers/fwu/fwu.h

@@ -11,5 +11,6 @@
 
 void fwu_init(void);
 bool fwu_is_trial_run_state(void);
+const struct fwu_metadata *fwu_get_metadata(void);
 
 #endif /* FWU_H */