irqchip/clps711x: Remove unused clps711x_intc_init() function

This function has no caller or declaration any more:

drivers/irqchip/irq-clps711x.c:215:13: error: no previous prototype for 'clps711x_intc_init'

The #ifdef check around clps711x_intc_init_dt() is also not
needed since the file is only built when that is enabled.

Fixes: 4a56f46a ("ARM: clps711x: Remove boards support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230516200516.554663-3-arnd@kernel.org