Remove MAX_REGISTER_SIZE from sh(64)-tdep.c

gdb/
	* sh-tdep.c (sh_pseudo_register_read): Remove
	MAX_REGISTER_SIZE.
	(sh_pseudo_register_write): Likewise.
	* sh64-tdep.c (sh64_pseudo_register_read): Likewise.
	(sh64_pseudo_register_write): Likewise.