ia64: remove unused __SLOW_DOWN_IO and SLOW_DOWN_IO definitions

Remove unused __SLOW_DOWN_IO and SLOW_DOWN_IO definitions.

Link: https://lkml.kernel.org/r/20221014001911.3342485-3-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/ia64/include/asm/io.h

@@ -23,10 +23,6 @@
 #include <asm/unaligned.h>
 #include <asm/early_ioremap.h>
 
-/* We don't use IO slowdowns on the ia64, but.. */
-#define __SLOW_DOWN_IO	do { } while (0)
-#define SLOW_DOWN_IO	do { } while (0)
-
 #define __IA64_UNCACHED_OFFSET	RGN_BASE(RGN_UNCACHED)
 
 /*