scripts: look for files with no licensing info

Bash hack that will parse the list of files known to git, filter the
ones for which we think we have licensing info, filter trivial ones
and print the non-compliant ones to stdout:

$ cd WHEREVER/zephyr.git
$ scripts/scan-no-license.sh  > no-license
I: 6327 files total
I: 3568 after filtering known issues
I: 3568 files before, 1828 after filtering token 'SPDX-License-Identifier'
I: 1828 files before, 1027 after filtering token 'Copyright'
I: 1027 files before, 1023 after filtering token 'License'
I: 1023 files before, 1017 after filtering token 'licenseText'
I: 1017 files before, 78 after filtering token '([Cc])'
I: 78 files without license
$ head no-license
arch/nios2/soc/nios2f-zephyr/cpu/ghrd_10m50da.qsys
arch/nios2/soc/nios2f-zephyr/cpu/ghrd_10m50da.qws
arch/nios2/soc/nios2f-zephyr/cpu/ghrd_10m50da.sof
arch/nios2/soc/nios2f-zephyr/cpu/ghrd_10m50da.sopcinfo
arch/nios2/soc/nios2f-zephyr/cpu/ghrd_10m50da_top.v
...

Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>