rx: memory allocation without checking for NULL return

	* elf32-rx.c (rx_elf_relocate_section): Use bfd_malloc rather than
	malloc.  Check for NULL return from bfd_malloc.
	(rx_table_find, rx_table_map): Likewise.
	(rx_set_section_contents): Check bfd_alloc return.
	(rx_dump_symtab): Don't alloc internal_syms or external_syms.