[IA64] fix IO_SPACE_SPARSE_ENCODING macro ambiguity

Parenthesize "p" to avoid ambiguity.  No callers have a problem today;
this is just to clean up the bad form.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/io.h

@@ -41,7 +41,7 @@
 #define IO_SPACE_BASE(space)		((space) << IO_SPACE_BITS)
 #define IO_SPACE_PORT(port)		((port) & (IO_SPACE_SIZE - 1))
 
-#define IO_SPACE_SPARSE_ENCODING(p)	((((p) >> 2) << 12) | (p & 0xfff))
+#define IO_SPACE_SPARSE_ENCODING(p)	((((p) >> 2) << 12) | ((p) & 0xfff))
 
 struct io_space {
 	unsigned long mmio_base;	/* base in MMIO space */