configure: switch to CONFIG_SOFTFLOAT for PPC

softfloat-native currently only supports one FPU context, while we need
at least 3 of them for the PPC target (FPU, SPE, AVR).
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6041 c046a42c-6fe2-441c-8c8c-71466251a162

configure

@@ -1654,6 +1654,8 @@ if test "$target_cpu" = "arm" \
      -o "$target_cpu" = "mipsn32el" \
      -o "$target_cpu" = "mips64" \
      -o "$target_cpu" = "mips64el" \
+     -o "$target_cpu" = "ppc" \
+     -o "$target_cpu" = "ppc64" \
      -o "$target_cpu" = "sparc" \
      -o "$target_cpu" = "sparc64" \
      -o "$target_cpu" = "sparc32plus"; then