gdb: make gdbarch_displaced_step_hw_singlestep return bool

gdb: make gdbarch_displaced_step_hw_singlestep return bool

Replace the int-used-as-a-bool with a bool.

gdb/ChangeLog:

	* gdbarch.sh (displaced_step_hw_singlestep): Return bool.
	* gdbarch.c: Re-generate.
	* gdbarch.h: Re-generate.
	* aarch64-tdep.c (aarch64_displaced_step_hw_singlestep): Return
	bool.
	* aarch64-tdep.h (aarch64_displaced_step_hw_singlestep):
	Likewise.
	* arch-utils.h (default_displaced_step_hw_singlestep): Likewise.
	* arch-utils.c (default_displaced_step_hw_singlestep): Likewise.
	* rs6000-tdep.c (ppc_displaced_step_hw_singlestep): Likewise.
	* s390-tdep.c (s390_displaced_step_hw_singlestep): Likewise.

Change-Id: I76a78366dc5c0afb03f8f4bddf9f4e8d68fe3114