HE: Extend BSS color support

HE: Extend BSS color support

The HE Operation field for BSS color consists of a disabled, a partial,
and 6 color bits. The original commit adding support for BSS color
considered this to be a u8. This commit changes this to the actual
bits/values.

This adds an explicit config parameter for the partial bit. The disabled
is set to 0 implicitly if a bss_color is defined.

Interoperability testing showed that stations will require a BSS color
to be set even if the feature is disabled. Hence the default color is 1
when none is defined inside the config file.

Signed-off-by: John Crispin <john@phrozen.org>