irqchip/jcore: Don't show Kconfig menu item for driver

Core drivers for J-Core SoCs will be selected implicitly via
CONFIG_SH_JCORE_SOC instead. Based on a corresponding change to the
clocksource/timer driver requested by Daniel Lezcano.

Signed-off-by: Rich Felker <dalias@libc.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: linux-sh@vger.kernel.org
Link: http://lkml.kernel.org/r/883a3d17084003e3cf21bab73ec12828fe4ff6c6.1476899495.git.dalias@libc.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>