create_config: simplify prefix=* block, remove CONFIG_QEMU_PREFIX

As now that block handles only the prefix variable, the code can be much
simpler. This also removes the CONFIG_QEMU_PREFIX define as it is not
used by any C code.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

scripts/create_config

@@ -23,13 +23,8 @@ case $line in
     eval "$name=\$define_value"
     ;;
  prefix=*)
-    name=${line%=*}
-    value=${line#*=}
-    define_name=`echo $name | LC_ALL=C tr '[a-z]' '[A-Z]'`
-    eval "define_value=\"$value\""
-    echo "#define CONFIG_QEMU_$define_name \"$define_value\""
     # save for the next definitions
-    eval "$name=\$define_value"
+    prefix=${line#*=}
     ;;
  CONFIG_AUDIO_DRIVERS=*)
     drivers=${line#*=}