powerpc/86xx: Drop unused CONFIG_MPC8610

The MPC8610 symbol used to be default y if MPC8610_HPCD, but since
MPC8610_HPCD was removed MPC8610 is now never used. Remove it.

Fixes: 248667f8 ("powerpc: drop HPCD/MPC8610 evaluation platform support")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231123032902.2760818-1-mpe@ellerman.id.au

arch/powerpc/platforms/86xx/Kconfig

@@ -52,10 +52,3 @@ config MPC8641
 	select MPIC
 	default y if GEF_SBC610 || GEF_SBC310 || GEF_PPC9A \
 			|| MVME7100
-
-config MPC8610
-	bool
-	select HAVE_PCI
-	select FSL_PCI if PCI
-	select PPC_UDBG_16550
-	select MPIC