lightnvm: pblk: fix rqd.error return value in pblk_blk_erase_sync

rqd.error is masked by the return value of pblk_submit_io_sync.
The rqd structure is then passed on to the end_io function, which
assumes that any error should lead to a chunk being marked
offline/bad. Since the pblk_submit_io_sync can fail before the
command is issued to the device, the error value maybe not correspond
to a media failure, leading to chunks being immaturely retired.

Also, the pblk_blk_erase_sync function prints an error message in case
the erase fails. Since the caller prints an error message by itself,
remove the error message in this function.

Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Reviewed-by: Javier González <javier@cnexlabs.com>
Reviewed-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>