[PATCH v2] riscv: Add support for SPI on Kendryte K210

[Rick Chen]

> This enables configs necessary for using SPI. The environment is saved to
> the very end of SPI flash. This is unlikely to be overwritten unless the
> entire flash is reprogrammed.
>
> This also supplies a default bootcommand. It loads an image and device tree
> from the first partition of the MMC. This is a minimal/least effort
> bootcmd, so suggestions (especially in the form of patches) are welcome. I
> didn't set up distro boot because I think it is unlikely that any
> general-purpose linux distros will ever be ported to this board.
>
> Signed-off-by: Sean Anderson <seanga2 at gmail.com>
> ---
> Sorry for the late follow-up Jagen.
>
> This patch was previously part of
> https://patchwork.ozlabs.org/project/uboot/list/?series=208443
>
> Changes in v2:
> - Add CONFIG_HUSH_PARSER to run the bootcmd
>   (In my haste I forgot to commit my changes)
>
>  board/sipeed/maix/Kconfig          |  16 ++
>  configs/sipeed_maix_bitm_defconfig |  11 +
>  doc/board/sipeed/maix.rst          | 319 ++++++++++++++++++++++++-----
>  include/configs/sipeed-maix.h      |   7 +-
>  4 files changed, 301 insertions(+), 52 deletions(-)

Reviewed-by: Rick Chen <rick at andestech.com>