staging: unisys: remove typedef for CHANNEL_HEADER

Switch everywhere that CHANNEL_HEADER, pCHANNEL_HEADER, or
ULTRA_CHANNEL_PROTOCOL was used, to struct channel_header.

Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>