irqchip: gic: Call handle_bad_irq() directly

Previously, the gic_handle_cascade_irq() function was calling the
ARM-specific do_bad_IRQ() function which calls handle_bad_irq() after
acquiring the desk->lock. Locking the cascaded IRQ desc is not needed
for error reporting, so just call handle_bad_irq() directly.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <rob.herring@calxeda.com>