iwlwifi-5000: update the byte count in SCD

This patch udpates the byte count of the frame in the registers of the
scheduler.
This patch also moves two defines in iwl-4965.h to a more appropriate
area in the file.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>