staging: r8188eu: remove MAX_CHANNEL_NUM_2G

The constants MAX_CHANNEL_NUM_2G and MAX_CHANNEL_NUM have the same
value. Remove MAX_CHANNEL_NUM_2G and fix the place where it is used.

Acked-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220102131141.12310-2-straube.linux@gmail.com


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