staging: wfx: fix missing headers

Each headers files should include every types it needs to compile (ie.
"gcc $CFLAGS -xc file.h" should compile)

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20220113085524.1110708-4-Jerome.Pouiller@silabs.com


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