Makefile: Align fit-dtb.blob and u-boot.itb by 64bits

Enabling MULTI_DTB_FIT and DTB_RESELECT can end up with multi DTBs in FIT
image placed and aligned only by 32bits (4bytes). Based on device tree
specification:
"Specifically, the memory reservation block shall be aligned to an 8-byte boundary
and the structure block to a 4-byte boundary."
is 64bit (8bytes) alignment required. That's why make sure that
fit-dtb.blob and u-boot.itb as our primary target images for Xilinx ZynqMP
are all 64bit aligned.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Makefile

@@ -1169,6 +1169,8 @@ MKIMAGEFLAGS_fit-dtb.blob = -f auto -A $(ARCH) -T firmware -C none -O u-boot \
 	-a 0 -e 0 -E \
 	$(patsubst %,-b arch/$(ARCH)/dts/%.dtb,$(subst ",,$(CONFIG_OF_LIST))) -d /dev/null
 
+MKIMAGEFLAGS_fit-dtb.blob += -B 0x8
+
 ifneq ($(EXT_DTB),)
 u-boot-fit-dtb.bin: u-boot-nodtb.bin $(EXT_DTB)
 		$(call if_changed,cat)
@@ -1431,6 +1433,7 @@ MKIMAGEFLAGS_u-boot.itb =
 else
 MKIMAGEFLAGS_u-boot.itb = -E
 endif
+MKIMAGEFLAGS_u-boot.itb += -B 0x8
 
 ifdef U_BOOT_ITS
 u-boot.itb: u-boot-nodtb.bin \