For boards that invert the SMC91x IRQ line (maybe an FPGA inverts it),
the set_irq_type() call can't assume IRQT_RISING.  These particular
boards currently use OMAP-specific calls to change the trigger type,
but the boards break when set_irq_type() stops being a NOP.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>