powerpc/82xx: Select FSL_SOC

It used to be impossible to select CONFIG_CPM2 without selecting
CONFIG_FSL_SOC at the same time because CONFIG_CPM2 was dependent
on CONFIG_8260 and CONFIG_8260 was selecting CONFIG_FSL_SOC.

But after commit eb5aa2137275 ("powerpc/82xx: Remove CONFIG_8260
and CONFIG_8272") CONFIG_CPM2 depends on CONFIG_PPC_82xx instead
but CONFIG_PPC_82xx doesn't directly selects CONFIG_FSL_SOC.

Fix it by forcing CONFIG_PPC_82xx to select CONFIG_FSL_SOC just
like already done by PPC_8xx, PPC_MPC512x, PPC_83xx, PPC_86xx.

Reported-by: Randy Dunlap <[e-mail]>
Fixes: eb5aa2137275 ("powerpc/82xx: Remove CONFIG_8260 and CONFIG_8272")
Signed-off-by: Christophe Leroy <[e-mail]>
Tested-by: Randy Dunlap <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://msgid.link/7ab51354[e-mail]

arch/powerpc/platforms/82xx/Kconfig

···
 menuconfig PPC_82xx
 	bool "82xx-based boards (PQ II)"
 	depends on PPC_BOOK3S_32
+	select FSL_SOC
 
 if PPC_82xx
 
···
 	bool "Embedded Planet EP8248E (a.k.a. CWH-PPC-8248N-VE)"
 	select CPM2
 	select PPC_INDIRECT_PCI if PCI
-	select FSL_SOC
 	select PHYLIB if NETDEVICES
 	select MDIO_BITBANG if PHYLIB
 	help
···
 	bool "Keymile MGCOGE"
 	select CPM2
 	select PPC_INDIRECT_PCI if PCI
-	select FSL_SOC
 	help
 	  This enables support for the Keymile MGCOGE board.