nouveau/firmware: Add missing kfree() of nvkm_falcon_fw::boot

nouveau/firmware: Add missing kfree() of nvkm_falcon_fw::boot

nvkm_falcon_fw::boot is allocated, but no one frees it. This causes a
kmemleak warning.

Make sure this data is deallocated.

Fixes: 2541626cfb79 ("drm/nouveau/acr: use common falcon HS FW code for ACR FWs")
Signed-off-by: Nam Cao <namcao@linutronix.de>
Cc: stable@vger.kernel.org
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patch.msgid.link/20251117084231.2910561-1-namcao@linutronix.de