sysinfo: Fix reports on ARM
    
    Due to a kernel commit (b4b8f770e), cpuinfo format has changed on
    ARMs. Firstly, 'Processor: ...' may not be reported, it's
    replaced by 'model name: ...'. Secondly, the "Processor" string
    may occur in CPU name, e.g. 'ARMv7 Processor rev 5 (v7l)'.
    Therefore, we must firstly look for 'model name' and then for
    'Processor' if not found.
    Moreover, lines in the cpuinfo file are shuffled, so we better
    not manipulate the pointer to start of internal buffer as we may
    lost some info.
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>