staging: hv: Doubled ringbuffer size for Hyper-v network driver

Double the default network ringsize buffer for Hyper-V network driver.
In very heavily loaded systems the there is a chance you run out of
ringbuffer space and error out.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>