android: boot: support bootconfig

android: boot: support bootconfig

Support Bootconfig feature.
- The bootconfig feature replaces the androidboot.*
  kernel cmdline options.

This was adapted from downstream [1] commit : 7af0a0506d4d ("cuttlefish:
support bootconfig parameters").

Link:[1] https://android.googlesource.com/platform/external/u-boot/

Signed-off-by: Safae Ouajih <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Reviewed-by: Mattijs Korpershoek <[email protected]>
Tested-by: Mattijs Korpershoek <[email protected]>