RISC-V: refresh defconfig

This patch updates defconfig using savedefconfig on Linux-4.19.  It is
intended to have no functional change.

Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>