feat(fwu): migrate FWU metadata structure to version 2

The latest version of the FWU specification [1] has changes to the
metadata structure. This is version 2 of the structure.

Primary changes include
 - bank_state field in the top level structure
 - Total metadata size in the top level structure
 - Image description structures now optional
 - Number of banks and images per bank values part of the structure

Make changes to the structure to align with version 2 of the structure
defined in the specification. These changes also remove support for
version 1 of the metadata structure.

[1] - https://developer.arm.com/documentation/den0118/latest/

Change-Id: I84b4e742e463cae92375dde8b4603b4a581d62d8
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
diff --git a/include/drivers/fwu/fwu.h b/include/drivers/fwu/fwu.h
index 9f18e22..1414fec 100644
--- a/include/drivers/fwu/fwu.h
+++ b/include/drivers/fwu/fwu.h
@@ -9,6 +9,10 @@
 
 #include <stdbool.h>
 
+#define FWU_BANK_STATE_ACCEPTED		0xFCU
+#define FWU_BANK_STATE_VALID		0xFEU
+#define FWU_BANK_STATE_INVALID		0xFFU
+
 void fwu_init(void);
 bool fwu_is_trial_run_state(void);
 const struct fwu_metadata *fwu_get_metadata(void);