staging: speakup: speakup_acntpc.c: style fixes

* Clean this file based on reports from checkpatch.pl.
* Eliminate the unused synth_readable macro.
* Convert function-like macros to inline functions.

Signed-off-by: Christopher Brannon <chris@the-brannons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>