This adds a console command to aid in depthcharge storage subsystem
debugging.

The actual console command name is 'storage', it is further qualified
by several subcommands:

  'init'

Accepts no arguments, initializes storage subsystem, based on the set
of block device controllers registered in the board initialization
file.

  'show'

Accepts no arguments, prints out the list of initialized devices with
their name. Each device gets assigned a number, which is used as the
reference by other storage subcommands.

The 'default' device in the list is marked by the asterisk in the
first column, after initialization device zero is the default device.
This can be changed by the 'dev' subcommand.

 'dev'

Accepts a single argument - the number of the device as reported by
the 'show' command above. Future storage subcommands will operate on
the device set by the 'dev' subcommand.

 'read <base blk> <num blks> <dest addr>'

Read data from the default storage device, starting at block <base
blk>, read <num blks> blocks total, placing result in memory at <dest
addr>.

BUG=chromium:338061
TEST=manual

   rambi: sto init
   Added USB disk 4.
   *  0: SDHCI fixed
      1: USB disk 4
      2: SDHCI card
   3 devices total
   rambi: sto dev 1
   USB disk 4
   rambi: sto show
      0: SDHCI fixed
   *  1: USB disk 4
     2: SDHCI card
   3 devices total
   rambi: md.b 0x11000000
   11000000: fa 31 c0 8e d8 8e d0 bc 00 7c 89 e6 06 57 8e c0    .1.......|...W..
   11000010: fb fc bf 00 06 b9 00 01 f3 a5 ea 1f 06 00 00 52    ...............R
   11000020: 52 b4 41 bb aa 55 31 c9 30 f6 f9 cd 13 72 13 81    R.A..U1.0....r..
   11000030: fb 55 aa 75 0d d1 e9 73 09 66 c7 06 47 07 b4 42    .U.u...s.f..G..B
   rambi: sto read 0x5000 1 0x11000000
   rambi: md.b 0x11000000
   11000000: 43 48 52 4f 4d 45 4f 53 02 00 00 00 01 00 00 00    CHROMEOS........
   11000010: b8 04 00 00 00 00 00 00 a0 02 00 00 00 00 00 00    ................
   11000020: 00 02 00 00 00 00 00 00 78 02 00 00 00 00 00 00    ........x.......
   11000030: 48 02 00 00 00 00 00 00 40 00 00 00 00 00 00 00    H.......@.......

Change-Id: Iae0ce3890999c91ae65f28c69c7441fb35b3fe09
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/184601


Reviewed-by: Stefan Reinauer <reinauer@chromium.org>