zbd: Fix build errors on Windows and MacOS

Including dirent.h is not needed, so remove it to avoid a compilation
error on Windows and MacOS. Also make sure that EREMOTEIO is defined as
some OSes do not have this error code.

Fixes: b76949618d55 ("fio: Generalize zonemode=zbd")
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>