Revert "Update min_sdk_version from SdkSpec to ApiLevel"

Revert submission 2457063

Reason for revert: Broken udc-dev

Reverted changes: /q/submissionid:2457063

Change-Id: Id6349fc1318877044af713c914a0afd437d3d2d5
diff --git a/android/apex.go b/android/apex.go
index 87bff74..358818f 100644
--- a/android/apex.go
+++ b/android/apex.go
@@ -845,7 +845,7 @@
 // ModuleWithMinSdkVersionCheck represents a module that implements min_sdk_version checks
 type ModuleWithMinSdkVersionCheck interface {
 	Module
-	MinSdkVersion(ctx EarlyModuleContext) ApiLevel
+	MinSdkVersion(ctx EarlyModuleContext) SdkSpec
 	CheckMinSdkVersion(ctx ModuleContext)
 }