rtw88: change max_num_of_tx_queue() definition to inline in pci.h

It's more reasonable to define max_num_of_tx_queue() as an inline function.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>