mfd: rt5033: Drop rt5033-battery sub-device

The fuel gauge in the RT5033 PMIC (rt5033-battery) has its own I2C bus
and interrupt lines. Therefore, it is not part of the MFD device
and needs to be specified separately in the device tree.

Fixes: 0b271258 ("mfd: rt5033: Add Richtek RT5033 driver core.")
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Jakob Hauser <jahau@rocketmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/6a8a19bc67b5be3732882e8131ad2ffcb546ac03.1684182964.git.jahau@rocketmail.com