rtlwifi: Prepare for reworking 5G channels

There are 3 drivers in this family that have 5G radios. Each of them
defines local copies of the available channels. This patch adds the
two arrays to the core driver.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>