libata: fix reading concurrent positioning ranges log

commit c745dfc5 upstream.

The concurrent positioning ranges log is not a fixed size and may depend
on how many ranges are supported by the device. This patch uses the size
reported in the GPL directory to determine the number of pages supported
by the device before attempting to read this log page.

This resolves this error from the dmesg output:
    ata6.00: Read log 0x47 page 0x00 failed, Emask 0x1

Cc: stable@vger.kernel.org
Fixes: fe22e1c2

 ("libata: support concurrent positioning ranges log")
Signed-off-by: Tyler Erickson <tyler.erickson@seagate.com>
Reviewed-by: Muhammad Ahmad <muhammad.ahmad@seagate.com>
Tested-by: Michael English <michael.english@seagate.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>