nanddump: robust pretty hexdump

nanddump: robust pretty hexdump

Adapted code from the linux kernel hex_dump_to_buffer() (lib/hexdump.c)
to provide a more robust hexdump for the pretty option. Now, nanddump
can print out any size of OOB (or page for that matter...) without
having to worry about non-multiples of 16.

This also provides ability to dump ASCII format next to the hex output
once additional command-line flags are added.

Tested with Samsung K9GAG08U0D

Signed-off-by: Brian Norris <norris@broadcom.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>