If the whole image already resides in DRAM, e.g. by starting the
image via the bootm handler we try to load the piggydata from storage,
which may well be different from our expected piggydata, already
present in DRAM.

Fix this by avoiding the special piggydata load function, but instead
load the whole image after DRAM is up and just replace the PBL part to
ensure we are still running the HAB validated code after TF-A hands
back control to our code in DRAM.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>