ath10k: fix 8th virtual AP interface with DFS

Firmware 10.x supports up to 8 virtual AP interfaces, but in a DFS
channel it was possible to create only 7 interfaces as ath10k internal
creates a monitor interface for DFS. Previous vdev map initialization
was missing enough space for 8 + 1 vdevs due to wrong define used and
that's why there was no space for 8th interface. Use the correct define
TARGET_10X_NUM_VDEVS with 10.x firmware to make it possible to create
the 8th virtual interface.

Signed-off-by: Bartosz Markowski <bartosz.markowski@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>