signed_hdmi_imx8m.bin is already signed and has a IVT header. It should not
be put in u-boot-spl-mkimage.signed.bin. Move it to head of flash.bin
following NXP imx-mkimage. Keeping it in u-boot-spl-mkimage.signed.bin also
consumes a lot of TCM space which is not expected.
While moving it to head of flash.bin, other changes are required,
u-boot.itb is put at sector 768 per defconfig, so u-boot.itb binman
offset should be updated and it should be moved out from binman section.
Also binman symbol address are updated, so need to subtract u-boot-spl
image_pos + CONFIG_SPL_TEXT_BASE to find the correct location of ddr phy
firmware.
Because there is 1KB padding in HDMI firmware, use 32KB when burning
flash.bin to sd card.
Signed-off-by: Peng Fan <peng.fan@nxp.com>