sandbox: defconfig: enable support of sandbox PMIC drivers

This commit enables:
- emulated i2c PMIC driver
- sandbox PMIC I/O driver
- sandbox PMIC's regulator driver

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested on sandbox:
Tested-by: Simon Glass <sjg@chromium.org>

configs/sandbox_defconfig

@@ -28,3 +28,10 @@ CONFIG_USB_EMUL=y
 CONFIG_USB_STORAGE=y
 CONFIG_DM_RTC=y
 CONFIG_CMD_UT_TIME=y
+CONFIG_ERRNO_STR=y
+CONFIG_DM_PMIC=y
+CONFIG_DM_PMIC_SANDBOX=y
+CONFIG_CMD_PMIC=y
+CONFIG_DM_REGULATOR=y
+CONFIG_DM_REGULATOR_SANDBOX=y
+CONFIG_CMD_REGULATOR=y