tty/serial: add eco32_uart serial driver

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
eco32: add note about removing early_printk
eco32: fault: add debug prints
eco32: fault: handle faults when user space is accessed from kernel

This makes use of the exception fixups that are present in
copy_/to_from_user and friends-

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
eco32: entry: preserve irq settings when kernel psw is set

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
eco32: finish off irq implementation

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
eco32: boot: enable interrupt controller and uart in eco32_generic.dts

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>