regulator: max20086: Change enable gpio to optional

regulator: max20086: Change enable gpio to optional

The enable pin can be configured as always enabled by the hardware. Make
the enable gpio request optional so the driver doesn't fail to probe
when `enable-gpios` property is not present in the device tree.

Cc: stable@vger.kernel.org
Fixes: bfff546aae50 ("regulator: Add MAX20086-MAX20089 driver")
Signed-off-by: João Paulo Gonçalves <jpaulo.silvagoncalves@gmail.com>
Link: https://patch.msgid.link/20250420-fix-max20086-v1-2-8cc9ee0d5a08@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>