This reverts commit e6595224.

These kinds of patches are only making the code worse.

Compilers don't care about the unnecessary check, but removing it makes
the code less obvious to a human.  The declaration of 'len' is more than
80 lines earlier, so a human won't easily see that 'len' is of an
unsigned type, so to a human the range check that checks against zero is
much more explicit and obvious.

Any tool that complains about a range check like this just because the
variable is unsigned is actively detrimental, and should be ignored.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>