ata: libata-scsi: fix timeout type in ata_scsi_park_store()

ata_scsi_park_store() passes its 'long input' variable (if it's >= 0) to
ata_deadline() that now takes 'unsigned int' -- eliminate unneeded implicit
cast...

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>