Unify the QString creation from udev return values (char*)

Change-Id: Ic69fd0d62d3097685bc8c3e25a7d8f6c696d7e2a
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>