nbench-byte: Fix license QA error

The license is not a common only and seems to be a 'free distribution'
license but without explicit rules about modification or similar. Due
that, we copied the license text from the README file and added it
onto nbench-byte license file.

This fixes following QA error:

,----
| WARNING: Recipe nbench-byte, LICENSE (freely distributable) 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>