fs/seq_file.c: delete small-value optimization

num_to_str() optimizes printing small integers [0..9], so the same check
higher in callchain is unnecessary.

Link: http://lkml.kernel.org/r/20170516204246.GA18123@avx2


Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>