staging: rtl8192u: delete unused function CAM_read_entry

Fix the sparse warning: symbol 'CAM_read_entry' was not declared. Should it be static?

The function CAM_read_entry is not used and therefore deleted.

Signed-off-by: Benedict Boerger <benedict.boerger@cs.tu-dortmund.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>