boot/uboot: fix hook to copy imx firmware files

Simplification has broken it. Fix it again.

Fixes: af99e7a5f3863049 ("boot/uboot: copy IMX firmware files to uboot package dir")

Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

boot/uboot/uboot.mk

@@ -194,7 +194,7 @@ define UBOOT_COPY_IMX_FW_FILES
 		cp $(BINARIES_DIR)/$(fw) $(@D)/
 	)
 endef
-UBOOT_PRE_BUILD_HOOKS += UBOOT_COPY_IMX_DDR_FIRMWARE
+UBOOT_PRE_BUILD_HOOKS += UBOOT_COPY_IMX_FW_FILES
 endif
 
 ifeq ($(BR2_TARGET_UBOOT_NEEDS_DTC),y)