nvidia: provide a working X .conf for igpu+nvidia and only nvidia.

A modified xorg.conf.d snippet that works in all setups that I tested:

 - NVIDIA as primary GPU
 - Intel as primary GPU and NVIDIA PRIME Render offload

It is very important that to make PRIME render offload working
the 'xf86-video-intel` pkg must not be installed. As explained
in the official NVIDIA documentation only the "modesetting" driver
is supported.

srcpkgs/nvidia/files/nvidia-drm-outputclass.conf

@@ -0,0 +1,18 @@
+Section "ServerLayout"
+  Identifier "layout"
+  Option "AllowNVIDIAGPUScreens"
+EndSection
+
+Section "OutputClass"
+    Identifier "intel"
+    MatchDriver "i915"
+    Driver "modesetting"
+EndSection
+
+Section "OutputClass"
+    Identifier "nvidia"
+    MatchDriver "nvidia-drm"
+    Driver "nvidia"
+    Option "AllowEmptyInitialConfiguration"
+    ModulePath "/usr/lib/nvidia/xorg"
+EndSection

srcpkgs/nvidia/template

@@ -48,11 +48,11 @@ do_install() {
 		vinstall nvidia_drv.so 755 usr/lib/xorg/modules/drivers
 
 		# GLX extension module for X
-		vinstall libglxserver_nvidia.so.${version} 755 usr/lib/xorg/modules/extensions
+		vinstall libglxserver_nvidia.so.${version} 755 usr/lib/nvidia/xorg
 		ln -sf libglxserver_nvidia.so.${version} \
-			${DESTDIR}/usr/lib/xorg/modules/extensions/libglxserver_nvidia.so
+			${DESTDIR}/usr/lib/nvidia/xorg/libglxserver_nvidia.so
 		ln -sf libglxserver_nvidia.so.${version} \
-			${DESTDIR}/usr/lib/xorg/modules/extensions/libglxserver_nvidia.so.1
+			${DESTDIR}/usr/lib/nvidia/xorg/libglxserver_nvidia.so.1
 
 		vinstall libnvidia-egl-wayland.so.1.1.4 755 usr/lib
 		ln -sf libnvidia-egl-wayland.so.1.1.4 \
@@ -138,19 +138,14 @@ do_install() {
 			-i ${DESTDIR}/usr/src/nvidia-${version}/dkms.conf
 
 		vmkdir /usr/share/X11/xorg.conf.d/
-		vinstall nvidia-drm-outputclass.conf 644 \
-			/usr/share/X11/xorg.conf.d 30-nvidia-drm-outputclass.conf
+		vinstall ${FILESDIR}/nvidia-drm-outputclass.conf 644 \
+			/usr/share/X11/xorg.conf.d 10-nvidia-drm-outputclass.conf
 
 		# Blacklist nouveau
 		vmkdir usr/lib/modprobe.d
 		echo "blacklist nouveau" > ${DESTDIR}/usr/lib/modprobe.d/nvidia.conf
 		chmod 644 ${DESTDIR}/usr/lib/modprobe.d/nvidia.conf
 
-		# Omit drm dracut module too
-		vmkdir usr/lib/dracut/dracut.conf.d
-		echo "omit_dracutmodules+=\" drm \"" > \
-		${DESTDIR}/usr/lib/dracut/dracut.conf.d/99-nvidia.conf
-
 		# License and documentation
 		vlicense LICENSE
 		vdoc README.txt README
@@ -261,7 +256,6 @@ nvidia-dkms_package() {
 	pkg_install() {
 		vmove usr/src
 		vmove usr/lib/modprobe.d
-		vmove usr/lib/dracut
 	}
 }
 nvidia-opencl_package() {