linux-firmware: liquidio: fix GPL compliance issue

Part of the code inside the lio_vsw_23xx.bin firmware image is under GPL,
but the LICENCE.cavium file neglects to indicate that.  However,
LICENCE.cavium does correctly specify the license that covers the other
Cavium firmware images that do not contain any GPL code.

Fix the GPL compliance issue by adding a new file, LICENCE.cavium_liquidio,
which correctly shows the GPL boilerplate.  This new file specifies the
licenses for all liquidio firmware, including the ones that do not have
GPL code.

Change the liquidio section of WHENCE to point to LICENCE.cavium_liquidio.

Reported-by: Florian Weimer <[email protected]>
Signed-off-by: Manish Awasthi <[email protected]>
Signed-off-by: Manoj Panicker <[email protected]>
Signed-off-by: Faisal Masood <[email protected]>
Signed-off-by: Felix Manlunas <[email protected]>
Signed-off-by: Josh Boyer <[email protected]>