ARM: dts: Remove PIN_INPUT for dm816x McSPI

On dm816x we have no PIN_INPUT vs PIN_OUTPUT configuration, there
are just pulls. Let's remove the bogus flags.

Cc: Brian Hutchinson <b.hutchman@gmail.com>
Cc: Matthijs van Duin <matthijsvanduin@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>