net: ethtool: fix off-by-one error in max RSS context IDs

net: ethtool: fix off-by-one error in max RSS context IDs

Both ethtool_ops.rxfh_max_context_id and the default value used when
 it's not specified are supposed to be exclusive maxima (the former
 is documented as such; the latter, U32_MAX, cannot be used as an ID
 since it equals ETH_RXFH_CONTEXT_ALLOC), but xa_alloc() expects an
 inclusive maximum.
Subtract one from 'limit' to produce an inclusive maximum, and pass
 that to xa_alloc().
Increase bnxt's max by one to prevent a (very minor) regression, as
 BNXT_MAX_ETH_RSS_CTX is an inclusive max.  This is safe since bnxt
 is not actually hard-limited; BNXT_MAX_ETH_RSS_CTX is just a
 leftover from old driver code that managed context IDs itself.
Rename rxfh_max_context_id to rxfh_max_num_contexts to make its
 semantics (hopefully) more obvious.

Fixes: 847a8ab18676 ("net: ethtool: let the core choose RSS context IDs")
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Link: https://patch.msgid.link/5a2d11a599aa5b0cc6141072c01accfb7758650c.1723045898.git.ecree.xilinx@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>