fsl-eula-unpack.bbclass: Avoid warning about wrong 'S' being set
The binary files packages provided by Freescale need to have the
specialized unpack method called before the OE-Core original one. This
unsures that the source is available when sanity tests are done.
This fixes following warning:
,----
| WARNING: .../libfslcodec/4.0.2-r0/libfslcodec-4.0.2 ('S') don't
| exist, you must set 'S' to a proper value
`----
Change-Id: Ie85c5b2abdc34449503b543e5fc8d8e914ac0c1c Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
