Ramdisk in the manifest, simplify initrd generation

We currently support loading a ramdisk for the primary. In fact, all
primaries are required to have one called 'initrd.img'. This makes
the ramdisk optional and specifies its filename in the manifest.

With that, generate_initrd.py loses the last remaining hardcoded
assumption about the structure of the Hafnium ramdisk. Refactor the
script and the build so that generate_initrd.py simply accepts a list of
(name in ramdisk, path on host) pairs.

Bug: 117551352
Change-Id: Iff2d70205940a1740c473d1cac34d5a05d6d6791
diff --git a/src/boot_flow/common.c b/src/boot_flow/common.c
index 586d3d2..b295824 100644
--- a/src/boot_flow/common.c
+++ b/src/boot_flow/common.c
@@ -87,8 +87,9 @@
  * Takes action on any updates that were generated.
  */
 bool boot_flow_update(struct mm_stage1_locked stage1_locked,
+		      const struct manifest *manifest,
 		      struct boot_params_update *p, struct memiter *cpio,
 		      struct mpool *ppool)
 {
-	return plat_boot_flow_update(stage1_locked, p, cpio, ppool);
+	return plat_boot_flow_update(stage1_locked, manifest, p, cpio, ppool);
 }