net: txgbe: Add build support for txgbe

Add doc build infrastructure for txgbe driver.
Initialize PCI memory space for WangXun 10 Gigabit Ethernet devices.

Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Link: https://lore.kernel.org/r/20220628095530.889344-1-jiawenwu@trustnetic.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>