[AVR32] Platform code for pata_at32

This patch adds platform code for PATA devices on the AP7000.

[hskinnemoen@atmel.com: board code left out for now since stk1000
	doesn't support IDE out of the box]
Signed-off-by: Kristoffer Nyborg Gregertsen <kngregertsen@norway.atmel.com>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>