gdb.trace: Deduplicate write_inferior_data_ptr.

gdb.trace: Deduplicate write_inferior_data_ptr.

This function is now basically identical to write_inferior_data_pointer,
remove it and change all references.

gdb/gdbserver/ChangeLog:

	* tracepoint.c (x_tracepoint_action_download): Change
	write_inferior_data_ptr to write_inferior_data_pointer.
	(cmd_qtstart): Likewise.
	(write_inferior_data_ptr): Remove.
	(download_agent_expr): Change write_inferior_data_ptr to
	write_inferior_data_pointer.
	(download_tracepoint_1): Likewise.
	(download_tracepoint): Likewise.
	(download_trace_state_variables): Likewise.