wifi: remove obsolete hostap driver

HostAP is an ISA/PCMCIA style 802.11b driver supporting only
wireless extensions, and some custom ioctls (already removed).
Some devices include a legacy PCI bridge but no DMA.

The driver was marked obsolete in 2016 and is highly unlikely
to still have any users.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <kvalo@kernel.org>