Remove the unused SkCachePreload_arm

src/opts/SkCachePreload_arm.h

-/*
- * Copyright 2012 The Android Open Source Project
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-#ifndef SkCachePreload_arm_DEFINED
-#define SkCachePreload_arm_DEFINED
-
-// This file defines macros for preload instructions for ARM. These macros
-// are designed to be embedded inside GNU inline assembly.
-// For the use of these macros, __ARM_USE_PLD needs to be enabled. The cache
-// line size also needs to be known (and needs to be contained inside
-// __ARM_CACHE_LINE_SIZE).
-#if defined(__ARM_USE_PLD)
-
-#define PLD(x, n)           "pld        [%["#x"], #("#n")]\n\t"
-
-#if __ARM_CACHE_LINE_SIZE == 32
-    #define PLD64(x, n)      PLD(x, n) PLD(x, (n) + 32)
-#elif __ARM_CACHE_LINE_SIZE == 64
-    #define PLD64(x, n)      PLD(x, n)
-#else
-    #error "unknown __ARM_CACHE_LINE_SIZE."
-#endif
-#else
-    // PLD is disabled, all macros become empty.
-    #define PLD(x, n)
-    #define PLD64(x, n)
-#endif
-
-#define PLD128(x, n)         PLD64(x, n) PLD64(x, (n) + 64)
-
-#endif  // SkCachePreload_arm_DEFINED