ata: pata_hpt37x: disable primary channel on HPT371

The HPT371 chip physically has only one channel, the secondary one,
however the primary channel registers do exist! Thus we have to
manually disable the non-existing channel if the BIOS hasn't done this
already. Similarly to the pata_hpt3x2n driver, always disable the
primary channel.

Fixes: 669a5db4

 ("[libata] Add a bunch of PATA drivers.")
Cc: stable@vger.kernel.org
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>