mb/google/kahlee: Enable Secure OS

Secure OS was disabled on Grunt devices since it isn't used.
This reduces the attack surface and is meant to mitigate potential
security risks. However, this prevents users from using an alternate OS.
Enable Secure OS upstream to allows users to use Windows, and ensure
that it is still disabled in the chromium repo.

BUG=b:287630343
TEST=Builds with Secure OS included.
Cq-Depend: chromium:4620881

Change-Id: I213aebc41cae300ecee8c01fc5c7687f7e7f5ee3
Signed-off-by: Jon Murphy <jpmurphy@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75874
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/mainboard/google/kahlee/Kconfig

@@ -145,8 +145,10 @@ config TPM_SPI_SPEED
 
 endif
 
-# Don't use AMD's Secure OS
+# Don't use AMD's Secure OS if ChromeOS build.
 config USE_PSPSECUREOS
-	def_bool n
+	bool
+	default n if CHROMEOS
+	default y
 
 endif # BOARD_GOOGLE_BASEBOARD_KAHLEE