wcn36xx: Use existing pointers in wcn36xx_smd_config_bss_v1

Two pointers are already defined in this function "bss" and "sta" which
point to fields within msg_body->bss_params.

We can substantially reduce the amount of extraneous text in this function
by making use of those pointers. This change makes the code easier to read
and modify.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200829033846.2167619-10-bryan.odonoghue@linaro.org