watchdog: fix nv_tco section mismatch

Fix section mismatch warning:
Mark the called nv_tco_getdevice() as __devinit, just like its caller.

WARNING: drivers/watchdog/nv_tco.o(.devinit.text+0x16): Section mismatch in reference from the function nv_tco_init() to the function .init.text:nv_tco_getdevice()
The function __devinit nv_tco_init() references
a function __init nv_tco_getdevice().
If nv_tco_getdevice is only used by nv_tco_init then
annotate nv_tco_getdevice with a matching annotation.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>