wifi: rtl8xxxu: Make some arrays const

All the initialisation tables, plus rtl8xxxu_rfregs.

Most of them were already static.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/9407f219-a7ba-676e-3d99-154d67b312d2@gmail.com