Rename the kRAW_SkEncodedFormat to kDNG_SkEncodedFormat as it is actually only used for DNG format

BUG=b/27587823
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1782913002

Review URL: https://codereview.chromium.org/1782913002
diff --git a/src/codec/SkAndroidCodec.cpp b/src/codec/SkAndroidCodec.cpp
index 7dfd64d..6c3efe0 100644
--- a/src/codec/SkAndroidCodec.cpp
+++ b/src/codec/SkAndroidCodec.cpp
@@ -47,7 +47,7 @@
             return new SkWebpAdapterCodec((SkWebpCodec*) codec.detach());
 #endif
 #ifdef SK_CODEC_DECODES_RAW
-        case kRAW_SkEncodedFormat:
+        case kDNG_SkEncodedFormat:
             return new SkRawAdapterCodec((SkRawCodec*)codec.detach());
 #endif
         default: