linux-firmware: Install NVIDIA firmware files

On a Dell OptiPlex 7071 with

    01:00.0 VGA compatible controller [0300]: NVIDIA Corporation TU104 [GeForce RTX 2080] [10de:1e82] (rev a1)

Linux 5.17.2 with nouveau logs

    nouveau 0000:01:00.0: gr: firmware unavailable
    nouveau 0000:01:00.0: sec2: firmware unavailable
    […]
    nouveau 0000:01:00.0: DRM: failed to create kernel channel, -22

and repeatedly reports:

    nouveau 0000:01:00.0: disp: head 00000040

So, install the NVIDIA firmware files, as [suggested by the
developers](https://gitlab.freedesktop.org/drm/nouveau/-/issues/168).

Adding all firmware files uses 4.2 MB.

    @sigusr2:~$ du -sh /lib/firmware/nvidia/
    4.2M	/lib/firmware/nvidia/

linux-firmware.be0

@@ -75,6 +75,7 @@ mee_install() {
   cp -ax ${S}/bnx2      $D/lib/firmware
   cp -ax ${S}/bnx2x     $D/lib/firmware
   cp -ax ${S}/i915      $D/lib/firmware
+  cp -ax ${S}/nvidia    $D/lib/firmware
   cp -ax ${S}/radeon    $D/lib/firmware
   cp -ax ${S}/rtl_nic   $D/lib/firmware
 }