x86/apic/uv: Make x2apic_extra_bits static

Not used outside of the UV apic source.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105219.725264153@linutronix.de

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -22,7 +22,7 @@
 #include <asm/uv/uv.h>
 #include <asm/apic.h>
 
-DEFINE_PER_CPU(int, x2apic_extra_bits);
+static DEFINE_PER_CPU(int, x2apic_extra_bits);
 
 static enum uv_system_type	uv_system_type;
 static bool			uv_hubless_system;