[rtl/icache] Fix an inconsistency in data output
[rtl/icache] Fix an inconsistency in data output

- valid_o could be asserted for one cycle then dropped when receiving
  rvalid data for a request which has branched into  the middle of a
  line.
- This fix keeps valid_o asserted by using the offset version of
  fill_rvd_cnt_q (fill_rvd_beat) to compare against fill_out_cnt_q
  (which is also offset by the branch).

Signed-off-by: Tom Roberts <f3b1a53ee1cbeb35a47033dea932030093853292@lowrisc.org>

AmbiML/ibex,lowRISC/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex,lowRISC/ibex,AmbiML/ibex