rtw88: pci: Add prototypes for .probe, .remove and .shutdown

Also strip out other duplicates from driver specific headers.

Ensure 'main.h' is explicitly included in 'pci.h' since the latter
uses some defines from the former.  It avoids issues like:

 from drivers/net/wireless/realtek/rtw88/rtw8822be.c:5:
 drivers/net/wireless/realtek/rtw88/pci.h:209:28: error: ‘RTK_MAX_TX_QUEUE_NUM’ undeclared here (not in a function); did you mean ‘RTK_MAX_RX_DESC_NUM’?
 209 | DECLARE_BITMAP(tx_queued, RTK_MAX_TX_QUEUE_NUM);
 | ^~~~~~~~~~~~~~~~~~~~

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

 drivers/net/wireless/realtek/rtw88/pci.c:1488:5: warning: no previous prototype for ‘rtw_pci_probe’ [-Wmissing-prototypes]
 1488 | int rtw_pci_probe(struct pci_dev *pdev,
 | ^~~~~~~~~~~~~
 drivers/net/wireless/realtek/rtw88/pci.c:1568:6: warning: no previous prototype for ‘rtw_pci_remove’ [-Wmissing-prototypes]
 1568 | void rtw_pci_remove(struct pci_dev *pdev)
 | ^~~~~~~~~~~~~~
 drivers/net/wireless/realtek/rtw88/pci.c:1590:6: warning: no previous prototype for ‘rtw_pci_shutdown’ [-Wmissing-prototypes]
 1590 | void rtw_pci_shutdown(struct pci_dev *pdev)
 | ^~~~~~~~~~~~~~~~

Cc: Yan-Hsuan Chuang <yhchuang@realtek.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201126133152.3211309-18-lee.jones@linaro.org