can: sja1000: fix compilation on x86

Since commit:
04df251 can: sja1000: Make sja1000_of_platform selectable and compilable on SPARC
the driver can be activated on non powerpc platform like x86 or sparc. Without
this patch the driver fails to compile on platform that don't define NO_IRQ,
like x86.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>