staging:r8188eu: replace cap_* definitions with native kernel WLAN_CAPABILITY_*

cap_* definitions duplicate WLAN_CAPABILITY_*. Remove cap_* definitions,
improve code consistency.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Link: https://lore.kernel.org/r/20210314090247.21181-4-insafonov@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>