mt76: mt76x0: Move tables used only by init.c to their own header file

Taking the same approach as initvals_phy.h.

Fixes the following W=1 kernel build warning(s):

 drivers/net/wireless/mediatek/mt76/mt76x0/initvals.h:218:35: warning: ‘mt76x0_dcoc_tab’ defined but not used [-Wunused-const-variable=]
 218 | static const struct mt76_reg_pair mt76x0_dcoc_tab[] = {
 | ^~~~~~~~~~~~~~~
 drivers/net/wireless/mediatek/mt76/mt76x0/initvals.h:86:35: warning: ‘mt76x0_bbp_init_tab’ defined but not used [-Wunused-const-variable=]
 86 | static const struct mt76_reg_pair mt76x0_bbp_init_tab[] = {
 | ^~~~~~~~~~~~~~~~~~~
 drivers/net/wireless/mediatek/mt76/mt76x0/initvals.h:48:35: warning: ‘mt76x0_mac_reg_table’ defined but not used [-Wunused-const-variable=]
 48 | static const struct mt76_reg_pair mt76x0_mac_reg_table[] = {
 | ^~~~~~~~~~~~~~~~~~~~
 drivers/net/wireless/mediatek/mt76/mt76x0/initvals.h:14:35: warning: ‘common_mac_reg_table’ defined but not used [-Wunused-const-variable=]
 14 | static const struct mt76_reg_pair common_mac_reg_table[] = {
 | ^~~~~~~~~~~~~~~~~~~~

Cc: Felix Fietkau <nbd@nbd.name>
Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Cc: Ryder Lee <ryder.lee@mediatek.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Stanislaw Gruszka <stf_xl@wp.pl>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-mediatek@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>