staging: rtl8821ae: fix sparse warning for static declarations

This patch fixes the following sparse warnings:

drivers/staging/rtl8821ae/pci.c:52:4: warning: symbol '_rtl_mac_to_hwqueue' was not declared. Should it be static?
drivers/staging/rtl8821ae/pci.c:365:6: warning: symbol 'rtl_pci_check_buddy_priv' was not declared. Should it be static?
drivers/staging/rtl8821ae/pci.c:409:6: warning: symbol 'rtl_pci_get_linkcontrol_field' was not declared. Should it be static?
drivers/staging/rtl8821ae/pci.c:1748:6: warning: symbol 'rtl_pci_deinit' was not declared. Should it be static?
drivers/staging/rtl8821ae/pci.c:1763:5: warning: symbol 'rtl_pci_init' was not declared. Should it be static?
drivers/staging/rtl8821ae/pci.c:1780:5: warning: symbol 'rtl_pci_start' was not declared. Should it be static?
drivers/staging/rtl8821ae/pci.c:1814:6: warning: symbol 'rtl_pci_stop' was not declared. Should it be static?
drivers/staging/rtl8821ae/pci.c:2105:21: warning: symbol 'hw_export' was not declared. Should it be static?

Signed-off-by: Mathieu OTHACEHE <m.othacehe@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>