powerpc/configs: Properly enable PAPR_SCM in pseries_defconfig

My commit to add PAPR_SCM to pseries_defconfig failed to add the
required dependencies, meaning the driver doesn't get built.

Add the required LIBNVDIMM=m.

Fixes: d6481a7195 ("powerpc/configs: Add PAPR_SCM to pseries_defconfig")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220901014253.252927-1-mpe@ellerman.id.au

arch/powerpc/configs/pseries_defconfig

@@ -40,6 +40,7 @@ CONFIG_PPC_SPLPAR=y
 CONFIG_DTL=y
 CONFIG_PPC_SMLPAR=y
 CONFIG_IBMEBUS=y
+CONFIG_LIBNVDIMM=m
 CONFIG_PAPR_SCM=m
 CONFIG_PPC_SVM=y
 # CONFIG_PPC_PMAC is not set