"invalid privilege" in firmware_get()

[Johannes Hofmann]

firmware_get() in the recently ported subr_firmware.c causes a panic
when loading a firmware image.
The patch below fixes the issue:

diff --git a/sys/kern/subr_firmware.c b/sys/kern/subr_firmware.c
index 0cf58a8..b103e8f 100644
--- a/sys/kern/subr_firmware.c
+++ b/sys/kern/subr_firmware.c
@@ -321,7 +321,7 @@ firmware_get(const char *imagename)
         */
        td = curthread;
        if (priv_check(td, PRIV_FIRMWARE_LOAD) != 0 ||
-           priv_check_cred(td->td_ucred, 0, 0)) {
+           priv_check_cred(td->td_ucred, PRIV_ROOT, 0)) {
                lockmgr(&firmware_lock, LK_RELEASE);
                kprintf("%s: insufficient privileges to "
                    "load firmware image %s\n", __func__, imagename);