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 <[e-mail]>
Cc: [e-mail]
Reviewed-by: Lyude Paul <[e-mail]>
Signed-off-by: Lyude Paul <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

drivers/gpu/drm/nouveau/nvkm/falcon/fw.c

···
 	nvkm_memory_unref(&fw->inst);
 	nvkm_falcon_fw_dtor_sigs(fw);
 	nvkm_firmware_dtor(&fw->fw);
+	kfree(fw->boot);
+	fw->boot = NULL;
 }
 
 static const struct nvkm_firmware_func