USB: gpio_vbus: remove IRQF_SAMPLE_RANDOM use

IRQF_SAMPLE_RANDOM has been scheduled for removal for years (it was
scheduled by July 2009, but not yet remvoed).

I'm not sure when it's going to take place, but would be better to
remove it now.  Thanks for scripts/checkpatch secretary.

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>