Specify error type in case of cpio header

If an error is recognized when cpio header is parsed,
print a useful error reason else a generic error.

Signed-off-by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Daniel Schnell <daniel.schnell.extern@ifm.com>
Use MAX_IMAGE_FNAME for filename size and increase SWUPDATE_GENERAL_STRING_SIZE

Signed-off-by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Daniel Schnell <daniel.schnell.extern@ifm.com>