SPI Host: FSM Bug CSID Switch

[crsystems]

The OpenTitan SPI host FSM contains a bug as it jumps to the WaitIdle state after receiving a command with a different CSID as the previous command. It therefore basically always skips the first command after a CSID change which this patch rectifies (OpenTitan does it the same way).

diff --git a/hw/vendor/lowrisc_opentitan/spi_host/rtl/spi_host_fsm.sv b/hw/vendor/lowrisc_opentitan/spi_host/rtl/spi_host_fsm.sv
index 4fb1360d..babb6138 100644
--- a/hw/vendor/lowrisc_opentitan/spi_host/rtl/spi_host_fsm.sv
+++ b/hw/vendor/lowrisc_opentitan/spi_host/rtl/spi_host_fsm.sv
@@ -290,7 +290,7 @@ module spi_host_fsm
           if (idle_cntr_q == 4'h0) begin
             prestall_st_d = WaitLead;
           end else begin
-            prestall_st_d = WaitIdle;
+            prestall_st_d = CSBSwitch;
           end
         end
         IdleCSBActive: begin