scripts/check_format: use version_lt to compare shfmt version

It turns out we have a function to compare version numbers.
It additionally handles cases like "3.0.10 > 3.0.9". The
previous code returned false, the new one returns true.

version_lt() actually tests for less or equal, so compare
against 3.1.0 - the real minimum shfmt version we need.

Change-Id: Ibd18c4505e5b81c0073a907f23c3fc034cfbafbe
Suggested-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/2574


Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>