pbl: Move piggy verification into pbl_barebox_uncompress() ...

piggy verification is a direct prerequisite of uncompressing the
piggydata, so move the verification there.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>

pbl: add sha256 and piggy verification to PBL ...

Extract the necessary functions from sha256 into a PBL headder and add a
verification function to the PBL. The function will be called before the
individual architectures decompress functions is run.

Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

pbl: Provide C macro to test if we are compiling the pbl ...

Provide IN_PBL as boolean constant which can be tested for in C.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

pbl: factorise decompressor ...

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>