doc: DEVICE_*_MATRIX_FILE specifies absolute paths

The fact that these variables are 'FILE' instead of 'FILES' is due to
historical changes, but updating comment to reflect this to avoid
confusion.

Bug: N/A
Test: N/A
Change-Id: I92b685eceaab99c7786384c08076dcf3bd087326
diff --git a/compatibility_matrices/Android.mk b/compatibility_matrices/Android.mk
index 96191c8..b88d40b 100644
--- a/compatibility_matrices/Android.mk
+++ b/compatibility_matrices/Android.mk
@@ -33,7 +33,7 @@
 LOCAL_SRC_FILES := compatibility_matrix.empty.xml
 else
 
-# DEVICE_FRAMEWORK_COMPATIBILITY_MATRIX_FILE specify an absolute path
+# DEVICE_FRAMEWORK_COMPATIBILITY_MATRIX_FILE specifies absolute paths
 LOCAL_GENERATED_SOURCES := $(DEVICE_FRAMEWORK_COMPATIBILITY_MATRIX_FILE)
 
 # Enforce that DEVICE_FRAMEWORK_COMPATIBILITY_MATRIX_FILE does not specify required HALs
@@ -77,7 +77,7 @@
 LOCAL_MODULE_CLASS := ETC
 LOCAL_MODULE_RELATIVE_PATH := vintf
 
-# DEVICE_PRODUCT_COMPATIBILITY_MATRIX_FILE specify an absolute path
+# DEVICE_PRODUCT_COMPATIBILITY_MATRIX_FILE specifies absolute paths
 LOCAL_GENERATED_SOURCES := $(DEVICE_PRODUCT_COMPATIBILITY_MATRIX_FILE)
 
 # Enforce that DEVICE_PRODUCT_COMPATIBILITY_MATRIX_FILE does not specify required HALs