igc: Fix typo in i225 LTR functions

The LTR maximum value was incorrectly written using the scale from
the LTR minimum value. This would cause incorrect values to be sent,
in cases where the initial calculation lead to different min/max scales.

Fixes: 707abf06 ("igc: Add initial LTR support")
Suggested-by: Dima Ruinskiy <dima.ruinskiy@intel.com>
Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Nechama Kraus <nechamax.kraus@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>