[WATCHDOG] at32ap700x_wdt.c - Fix compilation warnings

Fix warning:
* ISO C90 forbids mixed declarations and code
* passing argument 2 of ‘test_and_set_bit’ from incompatible pointer type
* passing argument 2 of ‘clear_bit’ from incompatible pointer type

Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: Andrew Morton <akpm@linux-foundation.org>