detect: Adding cpu version

On recent version of lshw, if the version string is not save, we are
facing a situation where the exact product description is not available.

before :
('cpu', 'physical_0', 'product', 'Core i5 (None)'),
('cpu', 'physical_0', 'vendor', 'Intel Corp.'),
   2.60GHz'),

after:
('cpu', 'physical_0', 'product', 'Core i5 (None)'),
('cpu', 'physical_0', 'vendor', 'Intel Corp.'),
('cpu', 'physical_0', 'version', 'Intel(R) Core(TM) i5-3320M CPU @ 2.60GHz'),