sparc: in handler_irq() rename irq parameter to pil

The generic irq support uses "irq" to identify the
virtual irq number. To avoid confusion rename the
argument to handler_irq() to pil to match the
name of the parameter in the PCR register.

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