device create: spi: convert device_create to device_create_drvdata

Switch over to use the shiny new device_create_drvdata() call
instead of the original device_create() calls, so this continues
to work after device_create() is  removed.

Note that this driver never had the race which motivated removing
the original call; it locked correctly.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>