regulator: rk808: remove unused rk808_reg_ops_ranges

After removing all uses of the range operations in a recent patch,
we get a warning about the symbol not being referenced anywhere:

drivers/regulator/rk808-regulator.c:306:29: 'rk808_reg_ops_ranges' defined but not used

This removes the now-unused structure along with the
rk808_set_suspend_voltage_range function that is only referenced from
rk808_reg_ops_ranges.

Fixes: afcd666d ("regulator: rk808: remove linear range definitions with a single range")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Brown <broonie@kernel.org>