sparc64: use {get,set}_irq_data for handler_data

{get,set}_irq_data uses the member "handler_data" in irq_data
which fits the naem of the datatype.
The change has no functional impact

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>