ASoC: remove copy of intlog10()

Merge series from Andy Shevchenko <andriy.shevchenko@linux.intel.com>:

The first three patches moves intlog10() to be available in entire
kernel. The last one removes copy of it in one driver. Besides already
good Lines of Code (LoC) statistics the upcoming users, if any, can
utilize the exported functions.

The series can be routed via ASoC tree (as Mauro suggested).

Note, int_log.h is separated from math.h due to licensing.
I dunno if we can mix two in a single header file. In any
case we may do it later on.