wifi: rtw89: phy: generalize valid bit of BSS color

The register fields of BSS color map and valid bit are in the same register
for existing chips, but coming WiFi 7 chips define another register to
set valid bit, so add a field to chip_info to reuse the code.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231016065115.751662-3-pkshih@realtek.com