ata: pata_serverworks: Avoid overwriting initialised field in 'serverworks_osb4_sht

Fixes the following W=1 kernel build warning(s):

 drivers/ata/pata_serverworks.c:257:18: warning: initialized field overwritten [-Woverride-init]
 drivers/ata/pata_serverworks.c:257:18: note: (near initialization for ‘serverworks_osb4_sht.sg_tablesize’)

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andre Hedrick <andre@linux-ide.org>
Cc: linux-ide@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210528090502.1799866-11-lee.jones@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>