arm: npcm: modify configuration for the NPCM7xx BMC.

Modify configuration and MakeFile
for the Nuvoton NPCM and NPCM7xx BMC.

[arnd: took this one late, since it fixes some build problems
 with the original commit]

Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>