ARM: OMAP: DRA7: Reuse the omap44xx_restart and fix the device instance

The omap44xx_restart used on omap4 and omap5 devices can be reused
on dra7 devices as well. The device instance however is different
across omap5 and dra7 as compared to omap4. So fix this for omap5
as well as dra7.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: R Sricharan <r.sricharan@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>