gpiolib: remove duplicate pin range code

Commit 69e1601bca88809dc118abd1becb02c15a02ec71
"gpiolib: provide provision to register pin ranges"

Introduced both of_gpiochip_remove_pin_range() and
gpiochip_remove_pin_ranges(). But the contents are exactly
the same so remove the OF one and rely on the range deletion
in the core.

Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>