GFS2: Increase the max number of ACLs

This patch increases the maximum number of ACLs from 25 to 300 for
a 4K block size. The value is adjusted accordingly if the block size
is smaller. Note that this is an arbitrary limit with a performance
tradeoff, and that the physical limit is slightly over 500.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>