check-package: check *.hash files

check-package: check *.hash files

Check each hash entry (see [1]) and warn when:
- it does not have three fields;
- its type is unknown;
- its length does not match its type;
- the name of the file contains a directory component.

[1] http://nightly.buildroot.org/#adding-packages-hash

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Thomas De Schampheleire <patrickdepinguin@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>