Add DSSS Parameter Set element only for 2.4 GHz

Add DSSS Parameter Set element only for 2.4 GHz

From IEEE 802.11:
The DSSS Parameter Set element is present within Beacon frames
generated by STAs using Clause 15, Clause 16, and Clause 18
PHYs.
The element is present within Beacon frames generated by STAs
using a Clause 19 PHY in the 2.4 GHz band.

Same is applied to the Probe Response frame.

Do not include the DSSS Parameters Set element when operating on other
bands.

Signed-off-by: Jurijs Soloveckis <jsoloveckis@maxlinear.com>