linux low: Make the arch code free arch_process_info

linux low: Make the arch code free arch_process_info

For the same reason as the previous patch, we need to make the
arch-specific code free the arch_process_info structure it allocates.

gdb/gdbserver/ChangeLog:

	* linux-low.h (struct linux_target_ops) <delete_process>: New
	field.
	* linux-low.c (linux_mourn): Call the_low_target.delete_process.
	* linux-aarch64-low.c (aarch64_linux_delete_process): New.
	(struct linux_target_ops): Add delete_process callback.
	* linux-arm-low.c (arm_delete_process): New.
	(struct linux_target_ops): Add delete_process callback.
	* linux-bfin-low.c (struct linux_target_ops): Likewise.
	* linux-crisv32-low.c (struct linux_target_ops): Likewise.
	* linux-m32r-low.c (struct linux_target_ops): Likewise.
	* linux-mips-low.c (mips_linux_delete_process): New.
	(struct linux_target_ops): Add delete_process callback.
	* linux-ppc-low.c (struct linux_target_ops): Likewise.
	* linux-s390-low.c (struct linux_target_ops): Likewise.
	* linux-sh-low.c (struct linux_target_ops): Likewise.
	* linux-tic6x-low.c (struct linux_target_ops): Likewise.
	* linux-tile-low.c (struct linux_target_ops): Likewise.
	* linux-x86-low.c (x86_linux_delete_process): New.
	(struct linux_target_ops): Add delete_process callback.
	* linux-xtensa-low.c (struct linux_target_ops): Likewise.