sysinfo: Fix reports on ARM

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>