staging:rtl8192u: Refactor member variable enabled - Style

The structure rt_dot11d_info contains a memeber variable 'enabled',
which causes a checkpatch issue as it is declared as being of type
bool. The type of the variable has been changed to a 'u8', to clear
the issue.

Additionally to aid searching for the member variable in code it
has been renamed from 'enabled' to 'dot11d_enabled'.

These are purely coding style changes which should not impact runtime
code execution.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>