ARM NAND I/O interface update

Modify the arm_nand_data struct to better support both read and
write operations while using the same struct.  An additional
field was added, and initialized, to record the last operation
so that the correct code can be loaded to the working area.

[dbrownell@users.sourceforge.net: merge init patch, tweak GPL note]

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

src/flash/nand/davinci.c

@@ -710,6 +710,7 @@ NAND_DEVICE_COMMAND_HANDLER(davinci_nand_device_command)
 
 	info->io.target = target;
 	info->io.data = info->data;
+	info->io.op = ARM_NAND_NONE;
 
 	/* NOTE:  for now we don't do any error correction on read.
 	 * Nothing else in OpenOCD currently corrects read errors,

src/flash/nand/orion.c

@@ -155,6 +155,7 @@ NAND_DEVICE_COMMAND_HANDLER(orion_nand_device_command)
 
 	hw->io.target = hw->target;
 	hw->io.data = hw->data;
+	hw->io.op = ARM_NAND_NONE;
 
 	return ERROR_OK;
 }