target-i386: switch to softfloat

This increase the correctness (precision, NaN values, corner cases) on
non-x86 machines, and add the possibility to handle the exception
correctly.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

configure

diff --git a/configure b/configure
index da2da04..f2eab30 100755
--- a/configure
+++ b/configure
@@ -3275,14 +3275,7 @@
   echo "TARGET_XML_FILES=$list" >> $config_target_mak
 fi
 
-case "$target_arch2" in
-  i386|x86_64)
-    echo "CONFIG_NOSOFTFLOAT=y" >> $config_target_mak
-    ;;
-  *)
-    echo "CONFIG_SOFTFLOAT=y" >> $config_target_mak
-    ;;
-esac
+echo "CONFIG_SOFTFLOAT=y" >> $config_target_mak
 
 if test "$target_user_only" = "yes" -a "$bflt" = "yes"; then
   echo "TARGET_HAS_BFLT=y" >> $config_target_mak