scripts/output-machine-list: wider column width for SoC

The SoC for cubox-i was causing an overflow in the SoC column, which
makes sphinx error out:

  source/machine-list.inc:1: ERROR: Malformed table.
  Text in column margin at line offset 11.

Here's the part which was causing problems:

=========================  ==================================================  ==========  ==========
         Machine             Name                                                 SoC        Layer
=========================  ==================================================  ==========  ==========
...
cubox-i                    SolidRun CuBox-i                                    i.MX6 Q/DL/S  meta-fsl-arm-extra
...

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>
release-notes: remove "linux-fslc" section

There's no easy way to obtain the list of features programmatically.

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>
scripts/bitbake-metadata2doc.py: use virtual/bootloader in write_u_boot_table (not virtual/kernel)

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>
bitbake metadata extraction: move recipes data to the 'recipes' field in the boards data structure

The boards data structure will need more machine-specific fields, so
we move recipes to a 'recipes' tree.

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>
bitbake-metadata2doc.py: add helper functions to check machine compatibility

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>
extract-bitbake-metadata.py: write SOC_FAMILY and COMPATIBLE_MACHINE data to the metadata file

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>