Staging: w35und: remove rxisr.c as dead code

The vRxTimerStart() function is never called nor does the timer do anything
useful so remove the code.

Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>