powerpc/mpc52xx: Don't select user-visible RTAS_PROC

Otherwise we might select it when its dependenices aren't enabled,
leading to a build break.

It's default y anyway, so will be on unless someone disables it
manually.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/52xx/Kconfig

@@ -33,7 +33,6 @@ config PPC_EFIKA
 	bool "bPlan Efika 5k2. MPC5200B based computer"
 	depends on PPC_MPC52xx
 	select PPC_RTAS
-	select RTAS_PROC
 	select PPC_NATIVE
 
 config PPC_LITE5200