staging: rtl8188eu: Move channel_table away from rtw_mlme_ext.h

staging: rtl8188eu: Move channel_table away from rtw_mlme_ext.h

Moved "static const struct channel_table[]" from include/rtw_mlme_ext.h
to core/rtw_ioctl_set.c because the latter is the only file that uses
that array of struct(s) in the whole driver. "make rtl8188eu/ W=1" output
several warnings about "'channel_table' defined but not used
[-Wunused-const-variable=]".

Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Link: https://lore.kernel.org/r/20210413102033.24781-1-fmdefrancesco@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>