arm.md (VUNSPEC_PREFETCH): Delete constant definition.

arm.md (VUNSPEC_PREFETCH): Delete constant definition.

* arm.md (VUNSPEC_PREFETCH): Delete constant definition.
(prefetch): Rewrite using PREFETCH RTL primitive.
* arm.h (arm_builtins): Delete ARM_BUILTIN_PREFETCH).
* arm.c (arm_init_builtins): Don't initialize a builtin for
__builtin_prefetch here.
(arm_expand_builtin): Dont expand __builtin_prefetch here.

From-SVN: r47790