MFC r347253:
Protect from infinite sw-reset loop in mlx5core.

Avoid an infinite software firmware reset loop that may be caused by a
hardware bug by limiting the maximum number of resets.
The counter between resets is reset by request for reset, and not by a
successful reset.
The interval between two resets can be configured via sysctl:
hw.mlx5.sw_reset_timeout
which is global to all mlx5 devices in the system.

Submitted by: slavash@
Sponsored by: Mellanox Technologies