Compared to da830-rtc compatibility am3352-rtc is more compatible to
the one in am437x. Hence adding the am3352-rtc compatible to cover the
entire feature set.

The ti,am4372-rtc has no Documentation and not used even in the driver
hence removing it.
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>