mfd: tps65911-comparator: Fix a build error

In 2012, we changed the tps65910 API and fixed most drivers but forgot
to update this one.

Fixes: 3f7e8275 ("mfd: Commonize tps65910 regmap access through header")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>