f2fs: enhance scalability of trace macro

Use __print_flags in show_bio_op_flags and show_cpreason instead of
__print_symbolic, it enables tracer function traverses and shows all
bits in the flag.

Additionally, add missing REQ_FUA into F2FS_OP_FLAGS.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>