arm: arch_timer: balance device_node refcounting

When we get the device_node for the arch timer, it's refcount is
automatically incremented in of_find_matching_node, but it is
never decremented.

This patch decrements the refcount on the node after we're finished
using it.
Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm/kernel/arch_timer.c

@@ -488,6 +488,8 @@ int __init arch_timer_of_register(void)
 	for (i = PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++)
 		arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
 
+	of_node_put(np);
+
 	/*
 	 * If no interrupt provided for virtual timer, we'll have to
 	 * stick to the physical timer. It'd better be accessible...