net/mlx5e: SHAMPO, Rework header allocation loop

The current loop code was based on the assumption
that there can be page leftovers from previous function calls.

This patch changes the allocation loop to make it clearer how
pages get allocated every MLX5E_SHAMPO_WQ_HEADER_PER_PAGE headers.
This change has no functional implications.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20241107194357.683732-13-tariqt@nvidia.com


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