Linux kernel coding style requires a size of 8 characters for both TAB and
indentation, and such value is embedded as magic value allover the
checkpatch script.

This makes hard to reuse the script by other projects with different
requirements in their coding style (e.g.  OpenOCD [1] requires TAB size of
4 characters [2]).

Replace the magic value 8 with a variable.

Add a command-line option "--tab-size" to let the user select a
TAB size value other than 8.

[1] http://openocd.org/
[2] http://openocd.org/doc/doxygen/html/stylec.html#styleformatSigned-off-by: NAntonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: NErik Ahlén <erik.ahlen@avalonenterprise.com>
Signed-off-by: NSpencer Oliver <spen@spen-soft.co.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Link: http://lkml.kernel.org/r/20200122163852.124417-3-borneo.antonio@gmail.comSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>