ARM: dts: osd3358-sm-red: group in the same phandle all its properties

Having a single phandle reference for rtc0, mmc0 and am335x_pinmux makes
the DTS well-ordered and therefore more readable.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
Signed-off-by: Tony Lindgren <tony@atomide.com>