iwlwifi: fix indirect write bug

Fix a bug in writing to indirect (periphery) registers; although
writes seem successful the data is not written to the desired
address). Also fix address mask for HBUS_TARG_PRPH_RADDR and
HBUS_TARG_PRPH_WADDR registers.

Signed-off-by: Amnon Paz <amnonX.paz@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>