ARM: OMAP: Change all cpu_is_* occurences to soc_is_* for id.c

Currently apart from dra7, omap5 and amx3 all the other SoCs
are identified using cpu_is_* functions which is not right since
they are all SoCs(System on Chips). Hence changing the SoC
identification code to use soc_is instead of cpu_is and keeping
defines for cpu_is where needed. This allows us to replace the
rest of cpu_is usage along with other fixes as needed.

Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Keerthy <j-keerthy@ti.com>
[tony@atomide.com: reworked the soc.h changes to minimum]
Signed-off-by: Tony Lindgren <tony@atomide.com>