sdm: Reduce severity of create_fd failure messages

- Valid file descriptors are not guaranteed in
  prepare phase. File descriptors are set to
  correct values in commit phase. In such cases,
  create_fd failures are false positives.

Change-Id: I91fbc5b407ee4f84290be8beb8bf036870f2cf4a
CRs-Fixed: 2218863
diff --git a/libdrmutils/drm_master.cpp b/libdrmutils/drm_master.cpp
index f0d14b1..96429e2 100644
--- a/libdrmutils/drm_master.cpp
+++ b/libdrmutils/drm_master.cpp
@@ -97,7 +97,7 @@
   uint32_t gem_handle = 0;
   int ret = drmPrimeFDToHandle(dev_fd_, drm_buffer.fd, &gem_handle);
   if (ret) {
-    DRM_LOGE("drmPrimeFDToHandle failed with error %d", ret);
+    DRM_LOGW("drmPrimeFDToHandle failed with error %d", ret);
     return ret;
   }