gdb: remove parameter of gdbarch_displaced_step_hw_singlestep

gdb: remove parameter of gdbarch_displaced_step_hw_singlestep

I noticed that the closure parameter of
gdbarch_displaced_step_hw_singlestep is never used by any
implementation of the method, so this patch removes it.

gdb/ChangeLog:

	* gdbarch.sh (displaced_step_hw_singlestep): Remove closure
	parameter.
	* aarch64-tdep.c (aarch64_displaced_step_hw_singlestep):
	Likewise.
	* aarch64-tdep.h (aarch64_displaced_step_hw_singlestep):
	Likewise.
	* arch-utils.c (default_displaced_step_hw_singlestep):
	Likewise.
	* arch-utils.h (default_displaced_step_hw_singlestep):
	Likewise.
	* rs6000-tdep.c (ppc_displaced_step_hw_singlestep):
	Likewise.
	* s390-tdep.c (s390_displaced_step_hw_singlestep):
	Likewise.
	* gdbarch.c: Re-generate.
	* gdbarch.h: Re-generate.
	* infrun.c (resume_1): Adjust.

Change-Id: I7354f0b22afc2692ebff0cd700a462db8f389fc1