Arm/AArch64: Split DISPLACED_MODIFIED_INSNS name clash

Arm/AArch64: Split DISPLACED_MODIFIED_INSNS name clash

Both targets define DISPLACED_MODIFIED_INSNS, each with different values.
Add ARM_ and AARCH64_ to the start of the name to prevent confusion.

No functionality changes.

gdb/ChangeLog:

	* aarch64-linux-tdep.c (aarch64_linux_init_abi): Use
	AARCH64_DISPLACED_MODIFIED_INSNS.
	* aarch64-tdep.c (struct aarch64_displaced_step_data)
	(aarch64_displaced_step_copy_insn): Likewise.
	* aarch64-tdep.h (DISPLACED_MODIFIED_INSNS): Rename from..
	(AARCH64_DISPLACED_MODIFIED_INSNS): ...to this.
	* arm-linux-tdep.c (arm_linux_cleanup_svc): Use
	ARM_DISPLACED_MODIFIED_INSNS.
	* arm-tdep.c (arm_gdbarch_init): Likewise.
	* arm-tdep.h (DISPLACED_MODIFIED_INSNS): Rename from..
	(ARM_DISPLACED_MODIFIED_INSNS): ...to this.
	(struct arm_displaced_step_closure): Use
	ARM_DISPLACED_MODIFIED_INSNS.