post_proc: fix copyright marking for bass_boost.h

Copyright marking for bass_boost.h updated date
for 2013-2014 to 2015 in change merged under
commit 5f15ff9b7dc319bd5937c2d401eaefeb83a3d1c1.
Fix it by updating copyright to 2013-2015.

Change-Id: If8986bcc7ffcfc68f2a06d2a0d5f71f13f52a017
1 file changed