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/ls1088aqds_qspi_SECURE_BOOT_defconfig b/configs/ls1088aqds_qspi_SECURE_BOOT_defconfig
index 9dc5f8d..d401b91 100644
--- a/configs/ls1088aqds_qspi_SECURE_BOOT_defconfig
+++ b/configs/ls1088aqds_qspi_SECURE_BOOT_defconfig
@@ -75,3 +75,4 @@
 CONFIG_RSA=y
 CONFIG_RSA_SOFTWARE_EXP=y
 CONFIG_EFI_LOADER_BOUNCE_BUFFER=y
+CONFIG_FSL_USE_PCA9547_MUX=y