agp: kill phys_to_gart() and gart_to_phys()

There seems to be no reason for these -- they're a 1:1 mapping on all
platforms.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

arch/ia64/include/asm/agp.h

@@ -17,10 +17,6 @@
 #define unmap_page_from_agp(page)	/* nothing */
 #define flush_agp_cache()		mb()
 
-/* Convert a physical address to an address suitable for the GART. */
-#define phys_to_gart(x) (x)
-#define gart_to_phys(x) (x)
-
 /* GATT allocation. Returns/accepts GATT kernel virtual address. */
 #define alloc_gatt_pages(order)		\
 	((char *)__get_free_pages(GFP_KERNEL, (order)))