x86/HVM: don't disable the REP emulation optimizations for regular IO

x86/HVM: don't disable the REP emulation optimizations for regular IO

Currently REP emulations optimizations remain disabled even if
the emulation does not happen as a result of a vm_event reply
requestion emulation (i.e. even for regular IO). This patch takes
emulate_each_rep into account only if emulation has been requested
by a vm_event-capable application, and is a noticeable speed
optimization for monitored guests.

Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tamas K Lengyel <tamas@tklengyel.com>
Acked-by: Jan Beulich <jbeulich@suse.com>