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>