nrf: Add support for printing data from flash

The USART driver fails if the data buffer is in flash, so it fails when
trying to print string literals.

Add an internal RAM buffer that is consecutively copied into and printed.

Change-Id: I37bc817d72658cbd77618793198d12b845743442
Signed-off-by: Øyvind Rønningstad <oyvind.ronningstad@nordicsemi.no>
1 file changed