drivers/platform/x86: Clarify the MRST IPC driver description slightly

Make it clear that this driver is only needed for embedded hardware,
not PCs.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 0ec796d..3e1b8a2 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -534,6 +534,7 @@
 	default y
 	---help---
 	  IPC is used to bridge the communications between kernel and SCU on
-	  some embedded Intel x86 platforms.
+	  some embedded Intel x86 platforms. This is not needed for PC-type
+	  machines.
 
 endif # X86_PLATFORM_DEVICES