ARM: OMAP2+: Pad SPL binary to 8-byte alignment before DTB

The OMAP2 SPL linker script (also used for K3 platforms) currently uses
a 4-byte alignment directive after the __u_boot_list section. This
alignment directive only advances the location counter without padding
the actual binary output.

When objcopy extracts u-boot-spl-nodtb.bin, it includes only actual
data, stopping at the last byte of __u_boot_list (e.g., 0x41c359fc),
not an aligned address (e.g., 0x41c35a00). So, when the FIT image
containing device trees is concatenated to the SPL binary, it gets
appended at this unaligned file size, causing libfdt validation failure.

To fix this, move the alignment directive into the __u_boot_list section
itself and make it 8-byte aligned as per DT spec. This forces the linker
to include padding as part of the section data, ensuring objcopy
includes the padding bytes in the binary and the appended FIT image
starts at an 8-byte aligned boundary.

Reported-by: Anshul Dalal <anshuld@ti.com>
Closes: https://lore.kernel.org/u-boot/DFJ950O0QM0D.380U0N16ZO19E@ti.com
Fixes: 0535e46d55 ("scripts/dtc: Update to upstream version v1.7.2-35-g52f07dcca47c")
Signed-off-by: Beleswar Padhi <b-padhi@ti.com>

arch/arm/mach-omap2/u-boot-spl.lds

@@ -35,9 +35,13 @@ SECTIONS
 	. = ALIGN(4);
 	__u_boot_list : {
 		KEEP(*(SORT(__u_boot_list*)));
+		/*
+		 * Ensure 8-byte alignment at the end of the last section before
+		 * DTB is appended, to satisfy DT spec alignment requirements
+		 */
+		. = ALIGN(8);
 	} >.sram
 
-	. = ALIGN(4);
 	__image_copy_end = .;
 	_end = .;
 	_image_binary_end = .;