ARM: vGIC: fix nr_irq definition

The global variable "nr_irqs" is used for x86 and some common Xen code.
To make the latter work easily for ARM, it was #defined to NR_IRQS.
This not only violated the common habit of capitalizing macros, but
also caused issues if one wanted to use a rather innocent "nr_irqs" as
a local variable name or as a function parameter.
Drop the optimization and make nr_irqs a normal variable for ARM also.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>

xen/arch/arm/irq.c

@@ -27,6 +27,8 @@
 #include <asm/gic.h>
 #include <asm/vgic.h>
 
+unsigned int __read_mostly nr_irqs = NR_IRQS;
+
 static unsigned int local_irqs_type[NR_LOCAL_IRQS];
 static DEFINE_SPINLOCK(local_irqs_type_lock);
 

xen/include/asm-arm/irq.h

@@ -31,7 +31,7 @@ struct arch_irq_desc {
 /* LPIs are always numbered starting at 8192, so 0 is a good invalid case. */
 #define INVALID_LPI     0
 
-#define nr_irqs NR_IRQS
+extern unsigned int nr_irqs;
 #define nr_static_irqs NR_IRQS
 #define arch_hwdom_irqs(domid) NR_IRQS