ata: ahci-imx: Fix MODULE_ALIAS

ata: ahci-imx: Fix MODULE_ALIAS

commit ff2242760c3bd125edd9ff89e86af5ae9132c4bd upstream.

'ahci:' is an invalid prefix, preventing the module from autoloading.
Fix this by using the 'platform:' prefix and DRV_NAME.

Fixes: e53baf4d2246 ("ahci_imx: add ahci sata support on imx platforms")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>