staging: wfx: drop legacy compatible values

Values "silabs,wfx-sdio" and "silabs,wfx-spi" are deprecated for a while
now. We take advantage of getting out of the staging tree to drop them
and start from a blank sheet.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20220113085524.1110708-30-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>