davinci: dm646x: Add IDE setup

This patch adds platform data and init function for IDE which could be called
from board specific file to register IDE device.

Note that for 594MHz device the transfer mode is limited to UDMA4 since ideclk
rate is less than 100 MHz, which forces udma_mask in palm_bk3710.c to UDMA4,
while for 729MHz device, it is UDMA5.

Signed-off-by: Hemant Pedanekar <hemantp@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>