Save the last cycle in GCM GHASH calculation
Well, the GCM tag can be rearranged as $Tag = (Len(C, A) \times H) \oplus \textit{Other Stuff}$; if the length of your ciphertext (and additional authentication data) is consistent, you could precompute $Len(C, A) \times H$, and xor that in along with everything else in the final step.

One note: the (add/multiply) that you do in cycle 6 has the side effect of multiplying the result of the GHASH from the ciphertext by $H$; if you eliminate that multiply, you'd need to somehow get the same effect.