powerpc/configs/64s: Drop SPLPAR which is default y

SPLPAR is default y since commit 20c0e826 ("powerpc/pseries:
Implement paravirt qspinlocks for SPLPAR"), so doesn't need to be in the
defconfig.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230414132415.821564-2-mpe@ellerman.id.au

arch/powerpc/configs/ppc64_defconfig

@@ -26,7 +26,6 @@ CONFIG_BLK_DEV_INITRD=y
 CONFIG_PROFILING=y
 CONFIG_PPC64=y
 CONFIG_NR_CPUS=2048
-CONFIG_PPC_SPLPAR=y
 CONFIG_DTL=y
 CONFIG_PPC_SMLPAR=y
 CONFIG_IBMEBUS=y