hwc: Fix fps calculation.

Fps is returned directly by the driver. No need of additional calculations.

Change-Id: I17bed4347f094b71340ca39e37b66fbcf9fdba9c
diff --git a/libhwcomposer/hwc.cpp b/libhwcomposer/hwc.cpp
index a065834..02b19b8 100644
--- a/libhwcomposer/hwc.cpp
+++ b/libhwcomposer/hwc.cpp
@@ -165,7 +165,7 @@
         value[0] = 0;
         break;
     case HWC_VSYNC_PERIOD:
-        value[0] = 1000000000.0 / m->fps;
+        value[0] = m->fps;
         ALOGI("fps: %d", value[0]);
         break;
     default: