davinci: add spi devices support for da830/omap-l137/am17x evm

This patch adds the on-board SPI flash device to the
DA830/OMAP-L137/AM17x EVM. It also registers the SPI flash
device to the MTD subsystem.

Based on SPI flash device support for MityDSP-L138F platform.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
[michael.williamson@criticallink.com: moved da830evm_spi0_pdata to devices-da8xx.c]
[michael.williamson@criticallink.com: moved da830evm_init_spi0 to devices-da8xx.c]
Signed-off-by: Michael Williamson <michael.williamson@criticallink.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>