tty: cyclades: cyz_interrupt is only used for PCI

tty: cyclades: cyz_interrupt is only used for PCI

When CONFIG_PCI is not set, enabling CONFIG_CYZ_INTR has no
practical effect other than generating a warning about an
unused function:

drivers/tty/cyclades.c:1184:20: warning: 'cyz_interrupt' defined but not used [-Wunused-function]
 static irqreturn_t cyz_interrupt(int irq, void *dev_id)

This adds a dependency to avoid that warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>