mtd-utils: Add new syntax to get devices by name

mtd-utils: Add new syntax to get devices by name

This introduces a new feature to the MTD command line utilities that
allows MTD devices to be referenced by name instead of device node. For
example this looks like:

> # Display info for the MTD device with name "data"
> mtdinfo mtd:data
> # Copy file to MTD device with name "data"
> flashcp /my/file mtd:data

This follows the syntax supported by the kernel which allows MTD
device's to be mounted by name[1].

Add the function mtd_find_dev_node() that accepts an MTD "identifier"
and returns the MTD's device node. The function accepts a string
starting with "mtd:" which it treats as the MTD's name. It then attempts
to search for the MTD, and if found maps it back to the /dev/mtdX device
node. If the string does not start with "mtd:", then assume it's the old
style and refers directly to a MTD device node.

The function is then hooked into existing tools like flashcp, mtdinfo,
flash_unlock, etc. To load in the new MTD parsing code in a consistent
way across programs.

[1] http://www.linux-mtd.infradead.org/faq/jffs2.html#L_mtdblock

Signed-off-by: Brandon Maier <brandon.maier@collins.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>