watchdog: Drop unnecessary include of miscdevice.h

After commit 487722cf (watchdog: Get rid of MODULE_ALIAS_MISCDEV
statements) the affected drivers no longer need to include miscdevice.h.
Only exception is rt2880_wdt.c which never needed it.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>