staging: wfx: drop unused WFX_LINK_ID_GC_TIMEOUT

The definition WFX_LINK_ID_GC_TIMEOUT is not used anymore since
commit d6aeba57

 ("staging: wfx: simplify the link-id allocation")

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200406111756.154086-2-Jerome.Pouiller@silabs.com


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