j721s2: dts: binman: Package tiboot3.bin, tispl.bin and u-boot.img

Support has been added for both HS-SE, HS-FS  and GP images.

HS-SE:
    * tiboot3-j721s2-hs-evm.bin
    * tispl.bin
    * u-boot.img

HS-FS:
    * tiboot3-j721s2-hs-fs-evm.bin
    * tispl.bin
    * u-boot.img

GP:
    * tiboot3.bin --> tiboot3-j721s2-gp-evm.bin
    * tispl.bin_unsigned
    * u-boot.img_unsigned

It is to be noted that the bootflow followed by J721S2 requires:

tiboot3.bin:
	* R5 SPL
	* R5 SPL dtbs
	* TIFS
	* board-cfg
	* pm-cfg
	* sec-cfg
	* rm-cfg

tispl.bin:
	* DM
	* ATF
	* OP-TEE
	* A72 SPL
	* A72 SPL dtbs

u-boot.img:
	* A72 U-Boot
	* A72 U-Boot dtbs

Reviewed-by: Simon Glass <sjg@chromium.org>
[afd@ti.com: changed output binary names appropriately]
Signed-off-by: Andrew Davis <afd@ti.com>
Signed-off-by: Neha Malcom Francis <n-francis@ti.com>