imx8ulp: build ahab

The ahab was missed to be compiled, so add it back.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/imx8ulp/Makefile b/arch/arm/mach-imx/imx8ulp/Makefile
index 2c9938f..f7692cf 100644
--- a/arch/arm/mach-imx/imx8ulp/Makefile
+++ b/arch/arm/mach-imx/imx8ulp/Makefile
@@ -5,6 +5,7 @@
 
 obj-y += lowlevel_init.o
 obj-y += soc.o clock.o iomux.o pcc.o cgc.o rdc.o
+obj-$(CONFIG_AHAB_BOOT) += ahab.o
 
 ifeq ($(CONFIG_SPL_BUILD),y)
 obj-y += upower/