ata: ahci_xgene: fix parameter types of xgene_ahci_poll_reg_val()

xgene_ahci_poll_reg_val() passes its 'unsigned long {interval|timeout}'
params verbatim to ata_{msleep|deadline}() that just take 'unsigned int'
param for the time intervals in ms -- eliminate unneeded implicit cast...

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