imx: hab: use unified rom section for mx6sx and mx6ul

Add CONFIG_ROM_UNIFIED_SECTIONS for mx6sx and mx6ul target
platforms to resolve corresponding HAB_RVT_BASE base address,
the RVT table contains pointers to the HAB API functions in
ROM code.

Signed-off-by: Adrian Alonso <aalonso@freescale.com>
diff --git a/arch/arm/cpu/armv7/mx6/Kconfig b/arch/arm/cpu/armv7/mx6/Kconfig
index 0b02e9e..273e209 100644
--- a/arch/arm/cpu/armv7/mx6/Kconfig
+++ b/arch/arm/cpu/armv7/mx6/Kconfig
@@ -23,10 +23,12 @@
 	bool
 
 config MX6SX
+	select ROM_UNIFIED_SECTIONS
 	bool
 
 config MX6UL
 	select SYS_L2CACHE_OFF
+	select ROM_UNIFIED_SECTIONS
 	bool
 
 choice