[spi_device] Add ASSERT_KNOWN

Added assertions of known state for output ports.

Signed-off-by: Eunchan Kim <eunchan@google.com>
diff --git a/hw/ip/spi_device/rtl/spi_device.sv b/hw/ip/spi_device/rtl/spi_device.sv
index f186500..4537806 100644
--- a/hw/ip/spi_device/rtl/spi_device.sv
+++ b/hw/ip/spi_device/rtl/spi_device.sv
@@ -562,5 +562,13 @@
 
   // make sure scanmode_i is never X (including during reset)
   `ASSERT_KNOWN(scanmodeKnown, scanmode_i, clk_i, 0)
+  `ASSERT_KNOWN(CioMisoEnOKnown, cio_miso_en_o, clk_i, !rst_ni)
+
+  `ASSERT_KNOWN(IntrRxfOKnown,         intr_rxf_o,         clk_i, !rst_ni)
+  `ASSERT_KNOWN(IntrRxlvlOKnown,       intr_rxlvl_o,       clk_i, !rst_ni)
+  `ASSERT_KNOWN(IntrTxlvlOKnown,       intr_txlvl_o,       clk_i, !rst_ni)
+  `ASSERT_KNOWN(IntrRxerrOKnown,       intr_rxerr_o,       clk_i, !rst_ni)
+  `ASSERT_KNOWN(IntrRxoverflowOKnown,  intr_rxoverflow_o,  clk_i, !rst_ni)
+  `ASSERT_KNOWN(IntrTxunderflowOKnown, intr_txunderflow_o, clk_i, !rst_ni)
 
 endmodule