gdbserver: Use pattern rule for objects from nat/

gdbserver: Use pattern rule for objects from nat/

gdb/gdbserver/ChangeLog:

	* Makefile.in (%.o: ../nat/%.c): New rule.
	(x86-dregs.o: ../nat/x86-dregs.c): Remove.
	(amd64-linux-siginfo.o: ../nat/amd64-linux-siginfo.c): Remove.
	(linux-btrace.o: ../nat/linux-btrace.c): Remove.
	(linux-osdata.o: ../nat/linux-osdata.c): Remove.
	(linux-procfs.o: ../nat/linux-procfs.c): Remove.
	(linux-ptrace.o: ../nat/linux-ptrace.c): Remove.
	(linux-waitpid.o: ../nat/linux-waitpid.c): Remove.
	(mips-linux-watch.o: ../nat/mips-linux-watch.c): Remove.
	(ppc-linux.o: ../nat/ppc-linux.c): Remove.
	(linux-personality.o: ../nat/linux-personality.c): Remove.
	(aarch64-linux-hw-point.o: ../nat/aarch64-linux-hw-point.c): Remove.
	(aarch64-linux.o: ../nat/aarch64-linux.c): Remove.
	(x86-linux.o: ../nat/x86-linux.c): Remove.
	(x86-linux-dregs.o: ../nat/x86-linux-dregs.c): Remove.
	(linux-namespaces.o: ../nat/linux-namespaces.c): Remove.