hwmon: (ina2xx) make regulator 'vs' support optional

hwmon: (ina2xx) make regulator 'vs' support optional

According to the 'ti,ina2xx' binding, the 'vs-supply' property is
optional. Use devm_regulator_get_enable_optional() to avoid a kernel
warning message if the property is not provided.

Co-developed-by: Florin Buica <florin.buica@nxp.com>
Tested-by: Enric Balletbo i Serra <eballetbo@kernel.org>
Signed-off-by: Florin Buica <florin.buica@nxp.com>
Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
Link: https://lore.kernel.org/r/20250409074529.2233733-1-ciprianmarian.costea@oss.nxp.com
[groeck: Use standard multi-line comment]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>