mfd/extcon: max77693: Remove unused extern declarations and max77693_dev members

Clean up the max77693 private header file by removing:
1. Left-overs from previous way of interrupt handling (driver uses
   regmap_irq_chip).
2. Unused members of struct 'max77693_dev' related to interrupts in
   extcon driver.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>