sata: fix sata command can not being executed bug

Commit d97dc8a0 separated the non-command code into its own file
which caused variable sata_curr_device can not be set to a correct
value.

Before commit d97dc8a0, variable sata_curr_device can be set
correctly in sata_initialize().
After commit d97dc8a0, sata_initialize() is moved out to its own file.
Accordingly, variable sata_curr_device is removed from sata_initialize()
too. This caused sata_curr_device never gets a chance to be set properly
which prevent other commands from being executed.

This patch sets variable sata_curr_device properly.

Fixes: d97dc8a0 (dm: sata: Separate the non-command code into its
 own file)

Signed-off-by: Tang Yuantian <yuantian.tang@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>