f2fs_gc_range may return error, so its caller
f2fs_allocate_pinning_section should determine whether
to do retry based on ist return value.
Also just do f2fs_gc_range when f2fs_allocate_new_section
return -EAGAIN, and check cp error case in f2fs_gc_range.
Signed-off-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>