staging: gasket: remove gasket_wait_sync()

This function is not called anywhere, so just remove it.

Also, as an added benifit, Arnd points out that it doesn't even work
properly:
	This code won't work correct during leap seconds or a concurrent
	settimeofday() call, and it probably doesn't do what the author intended
	even for the normal case, as it passes a timeout in nanoseconds but
	reads the time using a jiffies-granularity accessor.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>