ARM: OMAP2+: Kconfig: convert SOC_OMAPAM33XX to SOC_AM33XX

No need to have an OMAP prefix on these SoCs that are in the family
but arent' really called OMAP.

Simple rename: CONFIG_SOC_OMAPAM33XX --> CONFIG_SOC_AM33XX

No functional change.

Signed-off-by: Kevin Hilman <khilman@ti.com>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
[tony@atomide.com: updated for the driver config change also]
Signed-off-by: Tony Lindgren <tony@atomide.com>