jsm: Remove ch_cpstime field

Currently the field jsm_channel->ch_cpstime is defined but never
used, so this patch removes it.

Signed-off-by: Breno Leitão <leitao@linux.vnet.ibm.com>
Cc: Scott Kilau <Scott.Kilau@digi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>