to tell the TTY subsystem that the DMA buffer
is the size of the FIFO, otherwise things like tty_wait_until_sent()
will time out too early.  Keep (and use) the hardware value separately
from the port->fifosize.

This was part of a larger patch from Linus Walleij, with a little
modification.

Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
–~òÕ—&x