sepolicy: take sepolicy split in .mk

This value is always set to true in the core build
system. Removing reads of it so we can mark it as
obsolete.

Bug: 257176017
Test: build
Change-Id: Ie7a72496bd4712583944ed833cd4364c5e3c520b
diff --git a/build/soong/policy.go b/build/soong/policy.go
index 7c1aab2..d8c3ffb 100644
--- a/build/soong/policy.go
+++ b/build/soong/policy.go
@@ -151,7 +151,7 @@
 	if c.isTargetRecovery() {
 		return "false"
 	}
-	return strconv.FormatBool(ctx.DeviceConfig().SepolicySplit())
+	return strconv.FormatBool(true)
 }
 
 func (c *policyConf) compatibleProperty(ctx android.ModuleContext) string {