T-HEAD c9xx pmu only needs to clear OV bits of MCOUNTEROF when MOIP bit of MIP is set, so correct the MIP value check to avoid race conditions during processing interrupt. In addition, the S-mode scounterof only have OV bit set when the related bits of MCOUNTERWEN is set, so also configure MCOUNTERWEN to allow kernel to access valid SCOUNTEROF. Signed-off-by: haijiao.liu <haijiao.liu@sophgo.com>