config: riscv64: Add initial openeuler_defconfig

riscv inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7NK25

--------------------------------

This config is based on riscv64-config.all.final of
https://gitee.com/openeuler-risc-v/kernel.git


openEuler-22.03-LTS-SP2:5.10.0-153.1.0.80
generated by 'make olddefconfig', merged configs tested in kernel v6.1.19,
and cleanup compiler's indicators.

Signed-off-by: Mingzheng Xing <xingmingzheng@iscas.ac.cn>