qcacld-3.0: Modify condition to send 6GHz HE caps

The 6GHz HE capability macros were backported from kernel version 5.8
into 5.4, so change the check for kernel version to simply check for
the macro definition itself.

Change-Id: I86a9dfa964356ba65bd21ffef802042d442356bc
CRs-fixed: 2960286