PPC: fix dcbzl detection on OSX

Originally committed as revision 23955 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -2346,7 +2346,7 @@ elif enabled ppc; then
 
     enable local_aligned_8 local_aligned_16
 
-    check_asm dcbzl     '"dcbzl 0, 1"'
+    check_asm dcbzl     '"dcbzl 0, %0" :: "r"(0)'
     check_asm ibm_asm   '"add 0, 0, 0"'
     check_asm ppc4xx    '"maclhw r10, r11, r12"'
     check_asm xform_asm '"lwzx %1, %y0" :: "Z"(*(int*)0), "r"(0)'