tsc210x cleanup

tsc210x cleanup

This is mostly cleanup of the tsc210x patch, but some bugs were fixed so now
it works on tsc2101 too.  Also, a few issues are now noted in the code:

 Tool-reported:
  - Address checkpatch.pl issues in the original patch
  - And also "sparse" issues

 Previously wrong:
  - Cope with CONFIG_SOUND_MODULE
  - Register accessor routines will now return error codes
  - ... many callers now abort cleanly after errors
  - Don't depend on seeing only a rev #1 tsc2102 chip!
  - Add missing EXPORT_SYMBOL declarations

 Style issues:
  - BUG_ON() is strongly to be avoided
  - So are macros that capture variables
  - And needless casting from void pointers
  - And type punning
  - Use dev_*() for messaging where practical
  - Use u16 not uint16_t, etc
  - Various other whitespace issues
  - Avoid __FUNCTION__
  - Single-lines for file-top comments; no whole paths

 Object code size and Other cleanup:
  - Compile most strings out unless -DDEBUG is configured (saving space)
  - Move some code into exit sections (then it may well vanish, saving space)
  - Add some header comments

 Open issues:
  - Hwmon needs to know VREF and the chip type, and to scale its values
  - Upstream push should exclude audio until some version is working
  - Audio will needs to export symbols to modules, too
  - Lots of the I/O calls (especially audio) still don't handle errors
  - How could board init code get board-specific temp calibration data?

Also the Kconfig is more open-ended; tsc210x might in the future include the
tsc2100 and tsc2111, it doesn't need to be limited to tsc2101 and tsc2102.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>