[WATCHDOG] MIPS RM9000 on-chip watchdog device - patch 2

Reorganize source code so that it is structured as follows:
- Function prototypes
- Local variables
- Module arguments
- Interrupt handler
- Watchdog functions
- /dev/watchdog operations
- Shutdown notifier
- Kernel interfaces
- Init & exit procedures
- Device driver init & exit

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>