lightnvm: remove minor version check for 2.0

A minor version number increase should not break backwards
compatibility.

Fixes: 3cb98f84

 ("lightnvm: add minor version to generic geometry")
Reviewed-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>