csky: Fixup FAULT_FLAG_XXX param for handle_mm_fault

The past code only passes the FAULT_FLAG_WRITE into
handle_mm_fault and missing USER & DEFAULT & RETRY.

The patch references to arch/riscv/mm/fault.c, but there is no
FAULT_FLAG_INSTRUCTION in csky hw.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>