Fix incorrect usage of bool

A bool can't be < 0

Change-Id: Ie94ffadcb38c95214d1105c02610e59b4b2872b2
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>

core/jni/android/graphics/pdf/PdfEditor.cpp

@@ -124,7 +124,7 @@ static bool writeAllBytes(const int fd, const void* buffer, const size_t byteCou
 static int writeBlock(FPDF_FILEWRITE* owner, const void* buffer, unsigned long size) {
     const PdfToFdWriter* writer = reinterpret_cast<PdfToFdWriter*>(owner);
     const bool success = writeAllBytes(writer->dstFd, buffer, size);
-    if (success < 0) {
+    if (!success) {
         ALOGE("Cannot write to file descriptor. Error:%d", errno);
         return 0;
     }