i2c: pm_smbus: Add the ability to force block transfer enable

i2c: pm_smbus: Add the ability to force block transfer enable

The PIIX4 hardware has block transfer buffer always enabled in
the hardware, but the i801 does not.  Add a parameter to pm_smbus_init
to force on the block transfer so the PIIX4 handler can enable this
by default, as it was disabled by default before.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1534796770-10295-9-git-send-email-minyard@acm.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>