scripts: check headline of drivers commits

scripts: check headline of drivers commits

A driver patch under net should start with "net/<driver name>" or if
a patch touch multiple drivers, it should only start with "net:".
The same apply for crypto.
A patch touching all drivers (net + crypto) should start with "drivers:".

Longer prefixes like "net/mlx:" (for mlx4/mlx5) or "net/e1000/base:" are
handled by not checking the colon.

The directories doc/ and config/ are ignored because a driver patch
can modify them.

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>