ARM: OMAP: AM35xx: convert 3517 detection/flags to AM35xx

Currently cpu_is_omap3517() actually detects any device in the AM35x
family (3517 and no-SGX version 3505.)  To make it more clear what is
being detected, convert the names from 3517 to AM35xx.

This adds a new soc_is_am35xx() which duplicates the cpu_is_omap3517().
In order to avoid cross-tree dependencies with clock-tree changes,
cpu_is_omap3517() is left until the clock changes are merged,
at which point cpu_is_omap3517() will be completely removed.

Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
Tested-by: Vaibhav Hiremath <hvaibhav@ti.com>
Tested-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>
[tony@atomide.com: change to use soc_is_omap instead]
Signed-off-by: Tony Lindgren <tony@atomide.com>