configure: fix --cpu=nocona

Use x86_64_suggest instead of _select as otherwise fast_cmov being
disabled (as it should be for nocona) also disables x86_64 breaking
the build.

Originally committed as revision 21446 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1130,7 +1130,7 @@ ppc4xx_deps="ppc"
 
 vis_deps="sparc"
 
-x86_64_select="cmov fast_cmov"
+x86_64_suggest="cmov fast_cmov"
 amd3dnow_deps="mmx"
 amd3dnowext_deps="amd3dnow"
 mmx_deps="x86"