arm64: defconfig: Enable MAX8973 regulator

The Tegra210 Smaug board uses MAX77621 for both CPU & GPU rail. Note
that max8973 and max77621 share the same driver. So enable this driver
for the PMIC.
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/configs/defconfig

@@ -437,6 +437,7 @@ CONFIG_REGULATOR_GPIO=y
 CONFIG_REGULATOR_HI6421V530=y
 CONFIG_REGULATOR_HI655X=y
 CONFIG_REGULATOR_MAX77620=y
+CONFIG_REGULATOR_MAX8973=y
 CONFIG_REGULATOR_PWM=y
 CONFIG_REGULATOR_QCOM_RPMH=y
 CONFIG_REGULATOR_QCOM_SMD_RPM=y