sparc32, leon: code cleanup of timer/IRQ controller initialization

Cleaned up leon_init_timers() by removing unnecessary double checking
and one indentation level. Changed LEON_IMASK to LEON_IMASK(cpu).

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>