powerpc/embedded6xx: select MPC10X_BRIDGE only if PCI is set

When CONFIG_SMP is not set, CONFIG_BROKEN_ON_SMP is set, and
CONFIG_PCI is not set, there can be a kconfig warning:

WARNING: unmet direct dependencies detected for PPC_INDIRECT_PCI
  Depends on [n]: PCI [=n]
  Selected by [y]:
  - MPC10X_BRIDGE [=y]

To fix that, make the selects of MPC10X_BRIDGE be conditional
on PCI and use "imply" instead of "select".
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Suggested-by: Michael Ellerman <mpe@ellerman.id.au> # use "imply"
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230521225103.19197-1-rdunlap@infradead.org

arch/powerpc/platforms/embedded6xx/Kconfig

@@ -10,7 +10,7 @@ config LINKSTATION
 	select FSL_SOC
 	select PPC_UDBG_16550 if SERIAL_8250
 	select DEFAULT_UIMAGE
-	select MPC10X_BRIDGE
+	imply MPC10X_BRIDGE if PCI
 	help
 	  Select LINKSTATION if configuring for one of PPC- (MPC8241)
 	  based NAS systems from Buffalo Technology. So far only
@@ -24,7 +24,7 @@ config STORCENTER
 	select MPIC
 	select FSL_SOC
 	select PPC_UDBG_16550 if SERIAL_8250
-	select MPC10X_BRIDGE
+	imply MPC10X_BRIDGE if PCI
 	help
 	  Select STORCENTER if configuring for the iomega StorCenter
 	  with an 8241 CPU in it.