power: Convert CONFIG_PMIC_AS3722 to Kconfig

This converts the following to Kconfig:
   CONFIG_PMIC_AS3722

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/cei-tk1-som_defconfig b/configs/cei-tk1-som_defconfig
index 88b93cb..dd6fd49 100644
--- a/configs/cei-tk1-som_defconfig
+++ b/configs/cei-tk1-som_defconfig
@@ -38,6 +38,7 @@
 CONFIG_DM_PCI=y
 CONFIG_DM_PCI_COMPAT=y
 CONFIG_PCI_TEGRA=y
+CONFIG_PMIC_AS3722=y
 CONFIG_SYS_NS16550=y
 CONFIG_TEGRA114_SPI=y
 CONFIG_USB=y