icache: Reset FSM to FLUSH (#668)

The current implementation resets to IDLE, where the icache checks if it
was just enabled (rising edge of en_i), and flushes (initializes) itself
if so. This assumes that en_i is de-asserted during reset, which is not
necessarily the case (e.g. hardwired `en_i`), possibly leaving the cache
uninitialized. Hence, reset to FLUSH directly.

Signed-off-by: Nils Wistoff <nwistoff@iis.ee.ethz.ch>

src/cache_subsystem/cva6_icache.sv

@@ -457,7 +457,7 @@ end else begin : gen_piton_offset
       cmp_en_q      <= '0;
       cache_en_q    <= '0;
       flush_q       <= '0;
-      state_q       <= IDLE;
+      state_q       <= FLUSH;
       cl_offset_q   <= '0;
       repl_way_oh_q <= '0;
       inv_q         <= '0;