watchdog: at91sam9: at91_wdt_dt_ids cannot be __init

watchdog: at91sam9: at91_wdt_dt_ids cannot be __init

The device IDs are referenced by the driver and potentially
used beyond the init time, as kbuild correctly warns
about. Remove the __initconst annotation.

Without this patch, building at91_dt_defconfig results in:

WARNING: drivers/watchdog/built-in.o(.data+0x28): Section mismatch in reference from the variable at91wdt_driver to the (unknown reference) .init.rodata:(unknown)
The variable at91wdt_driver references
the (unknown reference) __initconst (unknown)

Signed-off-by: Arnd Bergmann <[email protected]>
Acked-by: Nicolas Ferre <[email protected]>
Tested-by: Fabio Porcedda <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>
Cc: [email protected]