fix typo in configure --help

Signed-off-by: NAndre Przywara <andre.przywara@amd.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

configure

@@ -674,7 +674,7 @@ echo "  --enable-bluez           enable bluez stack connectivity"
 echo "  --disable-kvm            disable KVM acceleration support"
 echo "  --enable-kvm             enable KVM acceleration support"
 echo "  --disable-nptl           disable usermode NPTL support"
-echo "  --enable-nptl            disable usermode NPTL support"
+echo "  --enable-nptl            enable usermode NPTL support"
 echo "  --enable-system          enable all system emulation targets"
 echo "  --disable-system         disable all system emulation targets"
 echo "  --enable-user            enable supported user emulation targets"