staging: r8188eu: improve timeout handling in rtw_check_join_candidate

Use the standard kernel functions to define and check the timeout in
rtw_check_join_candidate.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220409163212.241122-6-martin@kaiser.cx


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