IB/mlx5: Remove dead code in mr.c
IB/mlx5: Remove dead code in mr.c

In mlx5_mr_cache_init() the size variable is not used so remove it to
avoid compiler warnings when running with make W=1.

Signed-off-by: Eli Cohen <3ca62a2ad87376be2697209a1770e1afdbbba220@mellanox.com>
Signed-off-by: Roland Dreier <0d270388f2f92757a5de0f4bd891d3b392c44c4f@purestorage.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs