ath10k: advertize beacon_int_min_gcd

This patch fixes regression caused by 0c317a02
("cfg80211: support virtual interfaces with different beacon intervals"),
with this change cfg80211 expects the driver to advertize
'beacon_int_min_gcd' to support different beacon intervals in multivap
scenario. This support is added for, QCA988X/QCA99X0/QCA9984/QCA4019.

Verifed AP + mesh bring up on QCA9984 with beacon interval 100msec and
1000msec respectively.
Frimware: firmware-5.bin_10.4-3.5.3-00053

Fixes: 0c317a02 ("cfg80211: support virtual interfaces with different beacon intervals")
Signed-off-by: Anilkumar Kolli <akolli@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>