stdio: Pass device pointer to stdio methods

At present stdio device functions do not get any clue as to which stdio
device is being acted on. Some implementations go to great lengths to work
around this, such as defining a whole separate set of functions for each
possible device.

For driver model we need to associate a stdio_dev with a device. It doesn't
seem possible to continue with this work-around approach.

Instead, add a stdio_dev pointer to each of the stdio member functions.

Note: The serial drivers have the same problem, but it is not strictly
necessary to fix that to get driver model running. Also, if we convert
serial over to driver model the problem will go away.

Code size increases by 244 bytes for Thumb2 and 428 for PowerPC.

22: stdio: Pass device pointer to stdio methods
       arm: (for 2/2 boards)  all +244.0  bss -4.0  text +248.0
   powerpc: (for 1/1 boards)  all +428.0  text +428.0

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Marek Vasut <marex@denx.de>
Reviewed-by: Marek Vasut <marex@denx.de>