drm/nouveau: Improve message for missing firmware

drm/nouveau: Improve message for missing firmware

This is inteded to address concerns that users might get cryptic error
messages or a failure to boot if they set nouveau.config=NvGspRm=0 on
the kernel command line and their gpu requires gsp (Ada or newer).
With this patch, that configuration results in error messages like this:

nouveau 0000:01:00.0: gsp: Failed to load required firmware for device.
nouveau 0000:01:00.0: gsp ctor failed: -22
nouveau 0000:01:00.0: probe with driver nouveau failed with error -22

When nouveau fails to load like this, we still fall back to the generic
framebuffer device, so users will still have limited graphical output.

Signed-off-by: Mel Henning <mhenning@darkrefraction.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20250811213843.4294-4-mhenning@darkrefraction.com