mfd: silergy,sy7636a: Add config option MFD_SY7636A

mfd: silergy,sy7636a: Add config option MFD_SY7636A

Add a specific MFD_SY7636A config option.

As part of this change we can use MFD_SY7636A as a dependency for all
SY7636a components and also remove the name from MFD_SIMPLE_MFD_I2C as
it no longer needs to be selectable.

Signed-off-by: Alistair Francis <alistair@alistair23.me>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220525115554.430971-2-alistair@alistair23.me