evtchn: type adjustments

evtchn: type adjustments

First of all avoid "long" when "int" suffices, i.e. in particular when
merely conveying error codes. 32-bit values are slightly cheaper to
deal with on x86, and their processing is at least no more expensive on
Arm. Where possible use evtchn_port_t for port numbers and unsigned int
for other unsigned quantities in adjacent code. In evtchn_set_priority()
eliminate a local variable altogether instead of changing its type.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>