hwmon: (max6697) fix regmap leak on probe failure

hwmon: (max6697) fix regmap leak on probe failure

The i2c regmap allocated during probe is never freed.

Switch to using the device managed allocator so that the regmap is
released on probe failures (e.g. probe deferral) and on driver unbind.

Fixes: 3a2a8cc3fe24 ("hwmon: (max6697) Convert to use regmap")
Cc: stable@vger.kernel.org	# 6.12
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20251127134351.1585-1-johan@kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>