Add Android.bp variables to the soong build parser

* BtConfigIncludeDir: BOARD_BLUETOOTH_BDROID_BUILDCFG_INCLUDE_DIR
* BtHcilpIncluded: BOARD_BLUETOOTH_BDROID_HCILP_INCLUDED
* BtHciUseMct: BLUETOOTH_HCI_USE_MCT

Bug: 32958753
Test: Code compilation, no user visible effects

Change-Id: I0dc53172ee823e4e0fa69749e1297713796538cf
diff --git a/android/config.go b/android/config.go
index 7d268fc..6d28680 100644
--- a/android/config.go
+++ b/android/config.go
@@ -29,6 +29,7 @@
 )
 
 var Bool = proptools.Bool
+var String = proptools.String
 
 // The configuration file name
 const configFileName = "soong.config"
@@ -460,3 +461,15 @@
 	}
 	return *c.config.ProductVariables.DeviceVndkVersion
 }
+
+func (c *deviceConfig) BtConfigIncludeDir() string {
+	return String(c.config.ProductVariables.BtConfigIncludeDir)
+}
+
+func (c *deviceConfig) BtHcilpIncluded() string {
+	return String(c.config.ProductVariables.BtHcilpIncluded)
+}
+
+func (c *deviceConfig) BtHciUseMct() bool {
+	return Bool(c.config.ProductVariables.BtHciUseMct)
+}