enic: Bug fix: align desc ring sizes to 32 descs

Previous driver was aligning ring sizes to 16 descs, but hardware actually
wants desc ring sizes to be aligned to 32 descs.

Signed-off-by: Vasanthy Kolluri <vkolluri@cisco.com>
Signed-off-by: Scott Feldman <scofeldm@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>