net: ethernet: cisco: enic: enic_dev: Remove some unused functions

Removes some functions that are not used anywhere:
enic_dev_enable2_done() enic_dev_enable2() enic_dev_deinit_done()
enic_dev_init_prov2() enic_vnic_dev_deinit()

This was partially found by using a static code analysis program called cppcheck.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: David S. Miller <davem@davemloft.net>