brcmfmac: Remove the call to "dtim_assoc" IOVAR

When STA roams from one AP to another, after roam is complete, host
driver tries to get TIM information from firmware. This is no longer
supported in the firmware & hence, this call will always fail.
This failure results in the below message being displayed on the
console all the time when roam is done.

ieee80211 phy0: brcmf_update_bss_info: wl dtim_assoc failed (-52)

Changes ensure that the host driver will no longer try to get TIM
information from firmware.

Signed-off-by: Ramesh Rangavittal <ramesh.rangavittal@infineon.com>
Signed-off-by: Chi-hsien Lin <chi-hsien.lin@infineon.com>
Signed-off-by: Ian Lin <ian.lin@infineon.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220922104140.11889-5-ian.lin@infineon.com