Revert "Sets the BCDC priority to constant 0"

This reverts commit 8e4cdcb1.

Testing the latest wireless firmware and unable to replicate the
bug once this change is reverted.

Test used is :

Connect a Pi wirelessly to an AP (PiA), with another device
connected either wirelessly or via ethernet to the same
network (PiB).

On PiB run

sudo tcpdump -n 'udp port 7' -v -i wlan0

On PiA,

nc -T 0x10 -u <PiB ipaddress> 7

This sends a UDP packet to port 7, with the TOS flag set to 0x10.

Previously this would NOT arrive (or sometime be very badly delayed
 - 10's of seconds)

Sending TOS as 0

nc -T 0x0 -u <PiB ipaddress> 7

would arrive.

Now with the change reverted but the latest wireless firmware present
the tests works in all cases.