xserver-xorg: remove unknown configure options

Fix QA warning:

WARNING: QA Issue: xserver-xorg: configure was passed unrecognised
options: --disable-xshmfence --disable-libunwind --disable-dri3
[unknown-configure-option]

Signed-off-by: Javier Viguera <javier.viguera@digi.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>