rockchip: mkimage: enhance comments for v1 header

Improve the image header documentation for v1 header:

- specify this applies to all MMC, not only SD cards,
- specify the offset for SPI flashes,
- specify the key used for RC4 encoding,
- specify what "init" refers to, especially since some configs enable
  TPL,
- specify what "init_boot_size" refers to, especially since some configs
  enable TPL,
- specify the size of a block,
- add documentation for init_size and init_boot_size,

Note that the offset on the storage medium isn't necessarily 32KiB (64
blocks) for MMC or 0 for SPI flashes, it's just the first offset the
BootROM checks. Barebox[1] lists a few options, though those are
applicable to RK35xx which use the v2 header, so not guaranteed they can
be shared. On RK3399, the binary can at least be stored at offset 0 and
32KiB on SPI flashes.

[1] https://git.pengutronix.de/cgit/barebox/tree/arch/arm/mach-rockchip/bbu.c#n19

Signed-off-by: Quentin Schulz <[email protected]>
Reviewed-by: Kever Yang <[email protected]>

0 files changed, 0 insertions, 0 deletions