It is simpler for drivers to provide a ->device_reset() callback
irrespective of whether the GPIO, or firmware interface necessary to do the
reset, is discovered during probe.

Change ->device_reset() to return an error code.  Drivers that provide the
callback, but do not do the reset operation should return -EOPNOTSUPP.

Link: https://lore.kernel.org/r/20201103141403.2142-3-adrian.hunter@intel.comReviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Bean huo <beanhuo@micron.com>
Reviewed-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>