broadcom-nvram-config: Add compatible machine setting

This avoid a warning, during recipe parsing of bitbake, due an
incompatible machine as the nvram.txt is not available as no know
default one is suitable for every board so a specific one is need.

Change-Id: I409a1310c6f37975a46d79cdbd84665daa381e0d
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Merge "broadcom-nvram-config: Add compatible machine setting"