RISC-V: Enable PMEM drivers

We now have PMEM arch support available in RISC-V kernel so let us
enable relevant drivers in defconfig.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221114090536.1662624-4-apatel@ventanamicro.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/configs/defconfig

@@ -159,6 +159,7 @@ CONFIG_VIRTIO_MMIO=y
 CONFIG_RPMSG_CHAR=y
 CONFIG_RPMSG_CTRL=y
 CONFIG_RPMSG_VIRTIO=y
+CONFIG_LIBNVDIMM=y
 CONFIG_EXT4_FS=y
 CONFIG_EXT4_FS_POSIX_ACL=y
 CONFIG_EXT4_FS_SECURITY=y