This was caused by commit 16559ae48c76 ("kgdb: remove #include
<linux/serial_8250.h> from kgdb.h") from the tty tree.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>