core: set timeout to 400ms for secondary core disabling

The CONFIG_SECONDARY_CORE_DISABLING_TIMEOUT is for FW to do secondary
core disabling check and set to 5000ms by default. Linux driver
set ipc timeout duration to 500ms, but FW wait 5000ms in
cpu_disable_core for SET_DX ipc message. This makes driver stop but fw
is still waiting. Actually the disabling can be successful in far less
than 5000ms and it was first designed for FPGA case. Now change it to
400ms to make debugging easier.

Signed-off-by: Rander Wang <rander.wang@intel.com>

Author: RanderWang

src/platform/Kconfig

@@ -476,7 +476,7 @@ config SOF_STACK_SIZE
 
 config SECONDARY_CORE_DISABLING_TIMEOUT
 	int
-	default 5000
+	default 400
 	depends on MULTICORE
 	help
 	  Timeout value (in ms) for secondary core to enter D3 state.