dash: Fix license format QA error

This adds the & operator to fix the following QA error:

,----
| WARNING: Recipe dash, LICENSE (BSD GPLv2+) has invalid format,
|     LICENSES must have operator "([&|() ])" between them.
`----

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>