counter/ti-eqep: Fix regmap max_register

counter/ti-eqep: Fix regmap max_register

The values given were the offset of the register after the last
register instead of the actual last register in each range. Fix
by using the correct last register of each range.

Fixes: f213729f6796 ("counter: new TI eQEP driver")
Signed-off-by: David Lechner <david@lechnology.com>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/20201025165122.607866-1-david@lechnology.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>