board: freescale: ls2080a, ls2088a: 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>
[Squashed ls2088a patch to fix compilation]
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/configs/ls2081ardb_defconfig b/configs/ls2081ardb_defconfig
index 3a995e2..d775f56 100644
--- a/configs/ls2081ardb_defconfig
+++ b/configs/ls2081ardb_defconfig
@@ -65,3 +65,4 @@
 CONFIG_USB_XHCI_HCD=y
 CONFIG_USB_XHCI_DWC3=y
 CONFIG_EFI_LOADER_BOUNCE_BUFFER=y
+CONFIG_FSL_USE_PCA9547_MUX=y