power: reset: at91-reset: Fix module autoload

If the driver is built as a module, autoload won't work because the module
alias information is not filled. So user-space can't match the registered
device with the corresponding module.

Export the module alias information using the MODULE_DEVICE_TABLE() macro.

Before this patch:

$ modinfo drivers/power/reset/at91-reset.ko | grep alias
$

After this patch:

$ modinfo drivers/power/reset/at91-reset.ko | grep alias
alias:          of:N*T*Catmel,sama5d3-rstcC*
alias:          of:N*T*Catmel,sama5d3-rstc
alias:          of:N*T*Catmel,at91sam9g45-rstcC*
alias:          of:N*T*Catmel,at91sam9g45-rstc
alias:          of:N*T*Catmel,at91sam9260-rstcC*
alias:          of:N*T*Catmel,at91sam9260-rstc
alias:          platform:at91-sam9g45-reset
alias:          platform:at91-sam9260-reset

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>