net/mlx5: DR, Keep track of hot ICM chunks in an array instead of list

When ICM chunk is freed, it might still be accessed by HW until we do
sync with HW. This sync is expensive operation, so we don't do it often.
Instead, when the chunk is freed, it is moved to the buddy's "hot memory"
list. Once sync is done, we traverse the hot list and finally free all
the chunks.

It appears that traversing a long list takes unusually long time due to cache
misses on many entries, which causes a big "hiccup" during rule insertion.

This patch deals with this issue the following way:
 - Move hot chunks list from buddy to pool, so that the pool will
   keep track of all its hot memory.
 - Replace the list with pre-allocated array on the memory pool struct,
   and store only the information that is needed to later free this
   chunk in its buddy allocator.
   This cost additional memory for the array that is dynamically
   allocated, but it allows not to save long list of hot chunks,
   so at peak times it actually saves memory due to the fact that
   each array entry is much smaller than the chunk struct.

This way an overhead of traversing the long list is virtually removed:
the loop of freeing hot chunks takes ~27 msec instead of ~70 msec, where
most of it are the actual freeing activities.

Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>