staging: wfx: relax the PDS existence constraint

staging: wfx: relax the PDS existence constraint

The PDS file contains antenna parameters. The file is specific to each
hardware design. Normally, the board designer should add a line in the
of_device_id table with his own antenna parameters.

Until, now the absence of PDS file is a hard fatal error. However,
during the development, in most of the cases, an empty PDS file is
sufficient to start WiFi communication.

This patch keep an error, but allow the user to play with the device.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20210913130203.1903622-12-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>