docs: k1: no longer need to manually copy bootinfo_sd.bin

[Michael Opdenacker (michaelopdenacker)]

Description

This simplifies documentation for K1 based boards by removing a no longer necessary step.
Copy bootinfo_sd.bin at the beginning of the image is now taken care of by the "k1-image" class.

Checklist

• [ x] I have read and understood the Contributing Changes to a Component and Recipe Style Guide sections in the Yocto Project documentation
• [x ] I have tested this change (provide brief details below)
• [x ] Documentation has been added/updated where necessary in the README and docs/
• If the change is to a BSP in
  DEPRECATED.md,
  then it is maintenance-only, i.e. it does not add support for a
  previously-removed BSP (or significant features to one slated for removal)
• (For new/modified BSPs) I have added relevant information in the README table
• (For new/modified BSPs) The bitbake-setup templates in bitbake-registry/
  have been updated, if necessary
• (For new/modified BSPs) A kas file has been provided in kas/
• [ x] I have added my Signed-off-by and any other tags to each commit

How has this been tested?

This has been tested on the "orangepi-rv2" machine.
This should work the same on bananapi-f3 and bananapi-cm6-io which share the same SpacemiT K1 SoC.

[Trevor Gamblin (threexc)]

Thanks for this! I completely forgot to remove that when the class was added. LGTM.

[Khem Raj (kraj)]

lgtm