stagefright: fix finding hardware codec

When findMatchingCodecs(.., kHardwareCodecsOnly,..) was called,
it wouldn't actually match any hardware codecs because of a typo:

  if (!(TRUE_prefer_HW_codec && !FALSE_is_SW_codec))
    ==> if (!(TRUE && TRUE))

Fix logic and clarify statements

Change-Id: Ice725f043475caedd8f7ab961e0bc985db2eba6f
diff --git a/media/libstagefright/MediaCodecList.cpp b/media/libstagefright/MediaCodecList.cpp
index f75706b..8afb7e9 100644
--- a/media/libstagefright/MediaCodecList.cpp
+++ b/media/libstagefright/MediaCodecList.cpp
@@ -1165,7 +1165,9 @@
         CHECK(info != NULL);
         AString componentName = info->getCodecName();
 
-        if (!((flags & kHardwareCodecsOnly) && !isSoftwareCodec(componentName))) {
+        if ((flags & kHardwareCodecsOnly) && isSoftwareCodec(componentName)) {
+            ALOGV("skipping SW codec '%s'", componentName.c_str());
+        } else {
             matches->push(componentName);
             ALOGV("matching '%s'", componentName.c_str());
         }