ARM: iconnect: Remove include of removed linux/spi/orion_spi.h

v3.5-rc1 fails to build when DT and iconnect is enabled because of
this now none existant include file.

Also remove the other two SPI include files, which are not needed
with the move to DT.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Olof Johansson <olof@lixom.net>