nanddump: Refactor pretty print code into an sprintf()

nanddump: Refactor pretty print code into an sprintf()

A do-while loop in pretty_dump_to_buffer() can be refactored into a
single sprintf() statement. MAX() and MIN() are used to ensure that:
(1) We have at least a single space between hex and ASCII output
(2) We don't overflow the line buffer

This patch was suggested by Mike Frysinger.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>