staging: rtl8192e: Remove unchanged variable chan_forced

Remove unchanged variable chan_forced and equations that have always the
same result to shorten code.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/3f218531a9d31c399d1351d3da7f9ca13d20df0c.1681627603.git.philipp.g.hortmann@gmail.com


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