cxgbe tom: Remove orphaned function max_imm_tls_space().
Reported by: markj
Fixes: 789f2d4b3f33 cxgbe tom: Remove support for non-KTLS TLS offload.
Sponsored by: Chelsio Communications
(cherry picked from commit 6e26b4f8f4f6a9dd2a3ef88050108925f83dc460)