arm/dts: OMAP4: Add SPI controller nodes

Add the 4 McSPI controller nodes present in an OMAP4 device.

Remove SPI static device initialisation if DT is populated.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Rob Herring <rob.herring@calxeda.com>