audio_coding/codec/ilbc: Removed usage of WEBRTC_SPL_MUL_16_16_RSFT

The macro is defined as
#define WEBRTC_SPL_MUL_16_16_RSFT(a, b, c) \
    (WEBRTC_SPL_MUL_16_16(a, b) >> (c))

where the latter macro is in C defined as
(For definitions on ARMv7 and MIPS, see common_audio/signal_processing/include/spl_inl_{armv7,mips}.h)

The replacement consists of
- avoiding casts to int16_t if inputs already are int16_t
- adding explicit cast to <type> if result is assigned to <type> (other than int or int32_t)
- minor cleanups like remove of unnecessary parantheses and style changes

BUG=3348, 3353
TESTED=locally on Mac and trybots
R=kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/39139004

Cr-Commit-Position: refs/heads/master@{#8544}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8544 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/codecs/ilbc/window32_w32.c

@@ -53,10 +53,9 @@ void WebRtcIlbcfix_Window32W32(
     y_low = (int16_t)((y[i] - temp) >> 1);
 
     /* Calculate z by a 32 bit multiplication using both low and high from x and y */
-    temp = (x_hi * y_hi) << 1;
-    temp = (temp + (WEBRTC_SPL_MUL_16_16_RSFT(x_hi, y_low, 14)));
+    temp = ((x_hi * y_hi) << 1) + ((x_hi * y_low) >> 14);
 
-    z[i] = (temp + (WEBRTC_SPL_MUL_16_16_RSFT(x_low, y_hi, 14)));
+    z[i] = temp + ((x_low * y_hi) >> 14);
   }
 
   WebRtcSpl_VectorBitShiftW32(z, N, z, left_shifts);