power: isp1704_charger: Fix isp1704_write() definition

All calls to isp1704_write() are using parameter sequence of
isp1704_write(isp, reg, val) but the function is defined as
isp1704_write(isp, val, reg). Fix isp1704_write function definition so
that the driver to be functional.

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>