staging: r8188eu: move ODM_TARGET_CHNL_NUM_2G_5G

The ODM_TARGET_CHNL_NUM_2G_5G define is only used in one place, so move
it to the .c file it is used in instead of being in a .h file.

Link: https://lore.kernel.org/r/20210730092417.1014392-2-gregkh@linuxfoundation.org


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