qcacld-3.0: Remove csr_purge_vdev_all_ser_cmd_list()

Change I1d45de261c50f1835379a9cc1df4631f3e32f459 ("qcacld-3.0: Purge
all serialization commands on csr stop") removed the only client of
csr_purge_vdev_all_ser_cmd_list(). Since this function is now unused,
remove it.

Change-Id: I62ff513aa817d9b7fd4dcec156d53c02a1de40e2
CRs-Fixed: 2371198
2 files changed