microblaze: Use standard interrupt_init() function

Do not use microblaze specific interrupt init function.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/include/asm/microblaze_intc.h

@@ -34,5 +34,3 @@ struct irq_action {
  */
 int install_interrupt_handler(int irq, interrupt_handler_t *hdlr,
 				       void *arg);
-
-int interrupts_init(void);