net: netvsc: Update default VMBus channels

Change VMBus channels macro (VRSS_CHANNEL_DEFAULT) in
Linux netvsc from 8 to 16 to align with Azure Windows VM
and improve networking throughput.

For VMs having less than 16 vCPUS, the channels depend
on number of vCPUs. For greater than 16 vCPUs,
set the channels to maximum of VRSS_CHANNEL_DEFAULT and
number of physical cores / 2 which is returned by
netif_get_num_default_rss_queues() as a way to optimize CPU
resource utilization and scale for high-end processors with
many cores.
Maximum number of channels are by default set to 64.

Based on this change the channel creation would change as follows:

-----------------------------------------------------------------
| No. of vCPU |  dev_info->num_chn |    channels created        |
-----------------------------------------------------------------
|    1-16     |        16	   |          vCPU              |
|    >16      |  max(16,#cores/2)  | min(64 , max(16,#cores/2)) |
-----------------------------------------------------------------

Performance tests showed significant improvement in throughput:
- 0.54% for 16 vCPUs
- 0.83% for 32 vCPUs
- 0.86% for 48 vCPUs
- 9.72% for 64 vCPUs
- 13.57% for 96 vCPUs

Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://patch.msgid.link/1724735791-22815-1-git-send-email-ernis@linux.microsoft.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>