board: turris_mox: Add fixed regulator support to defconfig

Without this USB3 won't work in U-Boot.
Signed-off-by: NMarek Behun <marek.behun@nic.cz>
Reviewed-by: NStefan Roese <sr@denx.de>
Signed-off-by: NStefan Roese <sr@denx.de>

configs/turris_mox_defconfig

@@ -62,6 +62,8 @@ CONFIG_DEBUG_UART_SHIFT=2
 CONFIG_DEBUG_UART_ANNOUNCE=y
 CONFIG_MVEBU_A3700_UART=y
 CONFIG_MVEBU_A3700_SPI=y
+CONFIG_DM_REGULATOR=y
+CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_USB=y
 CONFIG_DM_USB=y
 CONFIG_USB_XHCI_HCD=y