Kconfig: Make HAVE_EM100_SUPPORT invisible

This is a property of a platform and should not be exposed to the
user.

Change-Id: I34f9097d40b2bf732cecf30bf13ba5a413dd53a5
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63676
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
diff --git a/src/Kconfig b/src/Kconfig
index d57ce90..dc81979 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -1210,7 +1210,7 @@
 	  `pragma Debug`.
 
 config HAVE_EM100_SUPPORT
-	bool "Platform can support the Dediprog EM100 SPI emulator"
+	bool
 	help
 	  This is enabled by platforms which can support using the EM100.