icd: add icd_format_is_equal()

It returns true when the formats are equal.
diff --git a/icd/common/icd-format.h b/icd/common/icd-format.h
index 614b8a3..9e1c29a 100644
--- a/icd/common/icd-format.h
+++ b/icd/common/icd-format.h
@@ -85,6 +85,12 @@
     }
 }
 
+static inline bool icd_format_is_equal(XGL_FORMAT a, XGL_FORMAT b)
+{
+    return (a.channelFormat == b.channelFormat &&
+            a.numericFormat == b.numericFormat);
+}
+
 static inline int icd_format_get_block_width(XGL_FORMAT format)
 {
     /* all compressed formats use 4x4 blocks */