platform/x86: thinkpad_acpi: Proper model/release matching

Modern Thinkpads have three character model designators. Previously, they
would be accepted, but recorded incompletely. Revision matching extracted
the wrong bytes from the ID string. This made the use of quirks for modern
machines impossible.

Fixes: 1b0eb5bc
Signed-off-by: Jouke Witteveen <j.witteveen@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>