driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

There is a limitation in hardware, if driver stop fetching packets
from rx ring, and the max ring bd number is set to 32768. Then
the FBD register value will remain 32768, which may block the hardware
receive unit.

This patch fixes it by reduce the max ring bd number to 32760.
Signed-off-by: Nshenjian (K) <shenjian15@huawei.com>
Reviewed-by: Nlipeng <lipeng321@huawei.com>
Reviewed-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>