staging: rtl8192su: remove extern keyword, remove static declaration

removed extern keyword from rtl819x_watchdog_wqcallback.
removed static declaration from variable check_reset_cnt.
changed NumRxOkInPeriod and NumTxOkInPeriod comparison
in function rtl819x_watchdog_wqcallback to 666; we're not on windows.
plus cosmetics.

Signed-off-by: Florian Schilhabel <florian.c.schilhabel@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>