virito-pci: fix OVERRUN problem

Overrunning array "proxy->guest_features" of 2 4-byte
elements at element index 2 (byte offset 8) using index
"proxy->gfselect" (which evaluates to 2). Normally, the
Linux kernel driver just read/write '0' or '1' as the
"proxy->gfselect" values, so using '<' instead of '=<' to
make coverity happy and avoid potential harm.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>