mem: add the swab (swap bytes) option to memory_display() ...

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

introduce spi command ...

usefull to debug spi

The command allow to read/write on a spi device

Usage: spi [OPTION] [data to write 0xXX]
write/read spi device.
  -b <bus_num>  spi bus number (default = 0)
  -r <count>    to read
  -c <cs>       chip select (default = 0)
  -m <mode>     spi mode (default = 0)
  -f <hz>       max_speed_hz (default = 1MHz)
  -w <bit>      bits_per_word (default = 8)
  -v            verbose

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>