[prim] Fix typo that caused fifo_async to get stuck

Signed-off-by: Timothy Chen <timothytim@google.com>
diff --git a/hw/ip/prim/rtl/prim_fifo_async.sv b/hw/ip/prim/rtl/prim_fifo_async.sv
index b58c30f..97fbc58 100644
--- a/hw/ip/prim/rtl/prim_fifo_async.sv
+++ b/hw/ip/prim/rtl/prim_fifo_async.sv
@@ -262,7 +262,7 @@
   end else if (Depth == 2) begin : g_simple_gray_conversion
 
     assign fifo_rptr_sync_combi = {fifo_rptr_gray_sync[PTR_WIDTH-1], ^fifo_rptr_gray_sync};
-    assign fifo_wptr_sync_combi = {fifo_wptr_gray_sync[PTR_WIDTH-1], ^fifo_rptr_gray_sync};
+    assign fifo_wptr_sync_combi = {fifo_wptr_gray_sync[PTR_WIDTH-1], ^fifo_wptr_gray_sync};
 
     assign fifo_rptr_gray_d = {fifo_rptr_d[PTR_WIDTH-1], ^fifo_rptr_d};
     assign fifo_wptr_gray_d = {fifo_wptr_d[PTR_WIDTH-1], ^fifo_wptr_d};