Change Ifff2ef2c8790994a68e676b8bba2fb03c21370d4 ("qcacld-3.0: Enable
station SMPS only if the session supported NSS > 1") introduced
function sme_is_sta_smps_allowed(). However this function has
subsequently never been used, so remove it.
Change-Id: I0a4d134986dd3a03d12e907f6df6ecb29b268eb3
CRs-Fixed: 2371155