Remove NULL checks before vfree() to fix these warnings:
./drivers/lightnvm/pblk-gc.c:27:2-7: WARNING: NULL check before some
freeing functions is not needed.
Signed-off-by: NTian Tao <tiantao6@hisilicon.com>
Signed-off-by: NMatias Bjørling <matias.bjorling@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>