Implement CPU model check to cut off false-positives

The code in intel_bug_present is known to produce much false-positives.
It is believed that the affected by the bug hardware are used with either Intel 80486 or Pentium.

Perform the check only when the kernel configured as CONFIG_X86_32,
then use cpuinfo_x86 of the first available CPU to check the model
and run initial check code.

Suggested-by: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>