Without this, a system using gcc (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu4)
aborts builds after reporting:

tcl.c: In function ‘handle_irscan_command’:
tcl.c:1168: warning: passing argument 1 of ‘buf_set_u32’ discards qualifiers from pointer target type

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