powerpc/cell/oprofile: Fix test on overlay_tbl_offset in vma_map

Offset is unsigned and when an address isn't found in the vma map
vma_map_lookup() returns the vma physical address + 0x10000000.

vma_map_lookup used to return 0xffffffff on a failed lookup, but
a change was made to return the vma physical address + 0x10000000
There are two callers of vam_map_lookup: one of them correctly
deals with this new return value, but the other (below) did not.
Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Acked-by: Maynard Johnson <maynardj@us.ibm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/oprofile/cell/vma_map.c

@@ -229,7 +229,7 @@ struct vma_to_fileoffset_map *create_vma_map(const struct spu *aSpu,
 	 */
 	overlay_tbl_offset = vma_map_lookup(map, ovly_table_sym,
 					    aSpu, &grd_val);
-	if (overlay_tbl_offset < 0) {
+	if (overlay_tbl_offset > 0x10000000) {
 		printk(KERN_ERR "SPU_PROF: "
 		       "%s, line %d: Error finding SPU overlay table\n",
 		       __func__, __LINE__);