staging: r8188eu: use in-kernel ieee channel

staging: r8188eu: use in-kernel ieee channel

Use the in-kernel structure and flags instead of defining a separate
one. The rtw_ieee80211_channel structure and flags can be replaced by
the ieee80211_channel defined in include/net/cfg80211.h since the flags
serve the same purpose and the ieee80211_channel struct includes the
elements used in the rtw_ieee80211_channel struct.

Signed-off-by: Solomon Tan <wjsota@gmail.com>
Link: https://lore.kernel.org/r/20220421235237.4218-1-wjsota@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>