board: freescale: ls1088a: Update I2C mux config

Updates the board configuration to enable use of the PCA9547 I2C mux.

Signed-off-by: Stephen Carlson <stcarlso@linux.microsoft.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/configs/ls1088ardb_tfa_defconfig b/configs/ls1088ardb_tfa_defconfig
index a3c7953..082578d 100644
--- a/configs/ls1088ardb_tfa_defconfig
+++ b/configs/ls1088ardb_tfa_defconfig
@@ -92,3 +92,4 @@
 CONFIG_USB_ETHER_ASIX88179=y
 CONFIG_USB_ETHER_RTL8152=y
 CONFIG_EFI_LOADER_BOUNCE_BUFFER=y
+CONFIG_FSL_USE_PCA9547_MUX=y