powerpc/xive: Define xive_do_source_eoi as static

Sparse shows that xive_do_source_eoi() file is defined without any
declaration, thus, it should be a static function.

	arch/powerpc/sysdev/xive/common.c:312:6: warning: symbol 'xive_do_source_eoi' was not declared. Should it be static?

This patch simply turns this symbol into static.
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/sysdev/xive/common.c

@@ -309,7 +309,7 @@ static void xive_do_queue_eoi(struct xive_cpu *xc)
  * EOI an interrupt at the source. There are several methods
  * to do this depending on the HW version and source type
  */
-void xive_do_source_eoi(u32 hw_irq, struct xive_irq_data *xd)
+static void xive_do_source_eoi(u32 hw_irq, struct xive_irq_data *xd)
 {
 	/* If the XIVE supports the new "store EOI facility, use it */
 	if (xd->flags & XIVE_IRQ_FLAG_STORE_EOI)