drm/panic: Fix expected string for QR_CODE in drm_panic_type_map

drm/panic: Fix expected string for QR_CODE in drm_panic_type_map

The help text of CONFIG_DRM_PANIC_SCREEN_QR_CODE documents the expected
value to CONFIG_DRM_PANIC_SCREEN as "qr_code" but drm_panic_type_map
checks for "qr". Adjust drm_panic_type_map and the module description to
match so that existing configurations do not stop working.

Fixes: e85e9ccf3f84 ("drm/panic: Report invalid or unsupported panic modes")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://lore.kernel.org/r/20260105-drm_panic-handle-invalid-drm_panic_screen-v1-2-55228bd4b0f8@kernel.org