irqchip/gic: Clear enable bits before restoring them

When restoring the GIC state (after a suspend/resume cycle,
for example), the driver directly writes the 'enabled' state
it has saved by accessing GICD_ISENABLERn, which performs
an OR operation between the value present in the register
and the value we write.

If whatever code that has run before we reentered the kernel
has enabled an interrupt that was previously disabled, we won't
restore that disabled state.

Making sure we first clear the register (by writting to
GICD_ICENABLERn) before restoring the enabled state.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Russell King <linux@arm.linux.org.uk>
Link: http://lkml.kernel.org/r/1447701208-18150-4-git-send-email-marc.zyngier@arm.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>