feat(fwu_metadata): add FWU metadata header and build options

Added a firmware update metadata structure as per section 4.1
in the specification document[1].

Also, added the build options used in defining the firmware
update metadata structure.

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

Change-Id: I8f43264a46fde777ceae7fd2a5bb0326f1711928
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/Makefile b/Makefile
index 4dbc2be..edc0d49 100644
--- a/Makefile
+++ b/Makefile
@@ -967,6 +967,8 @@
         ARM_ARCH_MINOR \
         BRANCH_PROTECTION \
         FW_ENC_STATUS \
+        NR_OF_FW_BANKS \
+        NR_OF_IMAGES_IN_FW_BANK \
 )))
 
 ifdef KEY_SIZE
@@ -1054,6 +1056,8 @@
         USE_SP804_TIMER \
         ENABLE_FEAT_RNG \
         ENABLE_FEAT_SB \
+        NR_OF_FW_BANKS \
+        NR_OF_IMAGES_IN_FW_BANK \
 )))
 
 ifeq (${SANITIZE_UB},trap)