f2fs: check validation of fault attrs in f2fs_build_fault_attr()

In the Linux kernel, the following vulnerability has been resolved:

f2fs: check validation of fault attrs in f2fs_build_fault_attr()

- It missed to check validation of fault attrs in parse_options(),

let's fix to add check condition in f2fs_build_fault_attr().

- Use f2fs_build_fault_attr() in __sbi_store() to clean up code.