greybus: tidy up svc_in_callback() and cport_in_callback()

The only use of local variable "es1" in in svc_in_callback() and
cport_in_callback() is to get at its hd field.  But we already have
that, so we can get rid of that local variable.

Also, rename the "cport" variable "cport_id" in cport_in_callback()
is to match the convention used elsewhere, and make it the proper
u16 type.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>