Octeontx2-pf: Fix Backpresure configuration

NIX block can receive packets from multiple links such as
MAC (RPM), LBK and CPT.

       -----------------
 RPM --|     NIX       |
       -----------------
             |
             |
            LBK

Each link supports multiple channels for example RPM link supports
16 channels. In case of link oversubsribe, NIX will assert backpressure
on receive channels.

The previous patch considered a single channel per link, resulting in
backpressure not being enabled on the remaining channels

Fixes: a7ef63db ("octeontx2-af: Disable backpressure between CPT and NIX")
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250617063403.3582210-1-hkelam@marvell.com


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