iwlifi: remove twice defined SINGLE_FRAME RX FH MASK

This patch removes second definition of FH_RCSR_CHNL0_RX_CONFIG_SINGLE_FRAME
in iwl-fh.h

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reported-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Acked-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>