Add ubiscan utility

Add ubiscan utility

ubiscan will scan the PEBs in a specific MTD device and print a summary of
the PEB erase counters and (optionally) details about each PEB's status.

Example output:

# ./ubiscan /dev/mtd6
Summary
=========================================================
mtd    : 6
type   : nand
size   : 110362624 bytes (105.2 MiB)
PEBs   : 842
min I/O: 2048 bytes

PEB erase counters
=========================================================
valid    : 834
empty    : 0
corrupted: 0
alien    : 0
bad      : 8

Histogram
=========================================================
from              to     count      min      avg      max
---------------------------------------------------------
0        ..        9:       55        1        4        9
10       ..       99:      174       10       48       99
100      ..      999:      514      103      287      987
1000     ..     9999:       91     1004     1880     2251
10000    ..    99999:        0        0        0        0
100000   ..      inf:        0        0        0        0
---------------------------------------------------------
Total               :      834        1      392     2251

If the --verbose switch is given, ubiscan will print PEB details:

# ./ubiscan --verbose /dev/mtd6

[... same output as before ...]

Details
=========================================================
PEB        0: 253
PEB        1: 1489
PEB        2: 1
PEB        3: 1
PEB        4: 1
PEB        5: 1
PEB        6: 1
PEB        7: 1
PEB        8: 1
PEB        9: 1
PEB       10: 1
...
PEB      832: 1225
PEB      833: 252
PEB      834: 111
PEB      835: 298
PEB      836: 1264
PEB      837: 11
PEB      838: EB_BAD
PEB      839: EB_BAD
PEB      840: EB_BAD
PEB      841: EB_BAD

Signed-off-by: Diego Ismirlian <dismirlian@gmail.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>