Remove unneeded variables and setting value to 0 on zero initialised
data and replace check for error with error_fatal. Rationalise loop
that sets PCI config header fields read only.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <e4caf35ca10a68f5c74ae3f93fa0bcfa9457beea.1610223397.git.balaton@eik.bme.hu>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>