ath10k: increase buffer len to print all wmi services

All wmi_services are not printing when we give below command.

cat /sys/kernel/debug/ieee80211/phyX/ath10k/wmi_services

This patch increases the buffer_len to 8192 to print all the wmi_services.

Signed-off-by: Tamizh chelvam <c_traja@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>