mlx4_core: Remove warning message about firmware bug

The kernel warning message added in commit 58d74bb1 ("mlx4_core:
Workaround firmware bug in query dev cap") about mlx4 reporting the
wrong number of "blue flame registers" doesn't really help anyone, since
the firmware bug is known and fixed and the bug is pretty much harmless
to users.  So just get rid of the warning.

Signed-off-by: Roland Dreier <rolandd@cisco.com>