thermal: int340x: Fix VCoRefLow MMIO bit offset for TGL

The VCoRefLow CPU FIVR register definition for Tiger Lake is incorrect.

Current implementation reads it from MMIO offset 0x5A18 and bit
offset [12:14], but the actual correct register definition is from
bit offset [11:13].

Update to fix the bit offset.

Fixes: 473be511 ("thermal: int340x: processor_thermal: Add RFIM driver")
Signed-off-by: Sumeet Pawnikar <sumeet.r.pawnikar@intel.com>
Cc: 5.14+ <stable@vger.kernel.org> # 5.14+
[ rjw: New subject, changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>