vpr200_tester: add extra diagnostic helpers to flash header

This adds compile time defines to output via UART when the
processor is doing the DCD block. This enables us to know that
a certain point of the boot stage was achieved.

Also add a special flash header to be used in conjunction with
the imx internal boot ROM.

Signed-off-by: Marc Reilly <marc@cpdesign.com.au>
common: console_simple: poller_call during ctrlc check

Signed-off-by: Marc Reilly <marc@cpdesign.com.au>
serial_imx.c: hack for poller framework in getc()

This hacks getc implementation so that poller_call is called while
waiting for chars.
(This is to make sure that a WDT feed hack is called regardless of
activity).

Signed-off-by: Marc Reilly <marc@cpdesign.com.au>
vpr200_tester: add wdt feeder based on polling framework

This adds a hook to feed the WDT. In some cases the WDT is enabled
outside of our control and cannot be disabled - thus must be fed.
(When loading via iROM serial bootloader)

Signed-off-by: Marc Reilly <marc@cpdesign.com.au>
vpr200_tester: add command to initialize sdram

If started via bootloader, the DCD entries in the flash header are
not done, so the SDRAM is not initialized.

This adds a command to do the SDRAM init manually. It should only
be invoked when running from internal RAM.

Signed-off-by: Marc Reilly <marc@cpdesign.com.au>