powerpc/85xx: add e500 HID1 bit definition

Also make 74xx HID1 definition conditional.

Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Shaohui Xie <b21989@freescale.com>
Cc: Roy Zang <tie-fei.zang@freescale.com>
Cc: Alexandre Bounine <alexandre.bounine@idt.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>