devicetree: fix build error on drivers/tty/serial/altera_jtaguart.c

This patch fixes the following build error caused by commit
85888069 ("tty: use of_match_ptr() for of_match_table entry").
The problem was a missing #include <linux/of.h> which is where
of_match_ptr() is defined.

drivers/tty/serial/altera_jtaguart.c:483:3: error: implicit declaration of function 'of_match_ptr' [-Werror=implicit-function-declaration]
drivers/tty/serial/altera_jtaguart.c:483:34: error: 'altera_jtaguart_match' undeclared here (not in a function)

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Tobias Klauser <tklauser@distanz.ch> (maintainer:ALTERA UART/JTAG...)
Cc: Alan Cox <alan@linux.intel.com> (maintainer:SERIAL DRIVERS)