autotools: Add tegra to AM_DISTCHECK_CONFIGURE_FLAGS

This allows the driver to be built on a make distcheck and makes sure
that it properly builds when a distribution tarball is made.

Suggested-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/Makefile.am b/Makefile.am
index 5c3a671..de6921b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -45,7 +45,7 @@
 	--enable-libunwind \
 	--with-platforms=x11,wayland,drm,surfaceless \
 	--with-dri-drivers=i915,i965,nouveau,radeon,r200,swrast \
-	--with-gallium-drivers=i915,nouveau,r300,pl111,r600,radeonsi,freedreno,svga,swrast,vc4,virgl,swr,etnaviv,imx \
+	--with-gallium-drivers=i915,nouveau,r300,pl111,r600,radeonsi,freedreno,svga,swrast,vc4,tegra,virgl,swr,etnaviv,imx \
 	--with-vulkan-drivers=intel,radeon
 
 ACLOCAL_AMFLAGS = -I m4