mod change 755 => 644 for multiple files

I executed 'find . -name "*.[chS]" -perm 755 -exec chmod 644 {} \;'

Signed-off-by: Thomas Weber <swirl@gmx.li>
Add some more: neither Makefile nor config.mk need execute permissions.
Signed-off-by: Wolfgang Denk <wd@denx.de>