sh-pfc: sh73a0: Remove EXT_IRQ16L and EXT_IRQ16H macros

The macros expand to irq_pin() calls and where most probably introduced
from a copy&paste of the sh7372 PFC data. Replace them with irq_pin().

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Magnus Damm <damm@opensource.se>