It's not always easy to know what is the size of a parition.

This patch adds the size of a memory range in human readable
format. We now have for example:

`---- cfi_flash0
     `---- nor0
          `---- 0x00000000-0x00ffffff (    16 MiB): /dev/nor0
          `---- 0x00000000-0x0001ffff (   128 KiB): /dev/env0
          `---- 0x00020000-0x0011ffff (     1 MiB): /dev/fpga0
          `---- 0x00120000-0x0019ffff (   512 KiB): /dev/self0
          `---- 0x001a0000-0x00d9ffff (    12 MiB): /dev/linux
          `---- 0x00da0000-0x00ffffff (   2.4 MiB): /dev/elf

Signed-off-by: Franck Jullien <franck.jullien@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>