powerpc/watchdog: Make default timeout for Book-E watchdog a Kconfig option

The PowerPC Book-E watchdog driver (booke_wdt.c) defines a default timeout
value in the code based on whether it's a Freescale Book-E part of not.
Instead of having hard-coded values in the driver, make it a Kconfig
option.

As newer chips gets faster, the current default values become less
appropriate, since the timeout sometimes occurs before the kernel finishes
booting.  Making the value a Kconfig option allows BSPs to configure a new
value without requiring the wdt_period command-line parameter to be set.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/drivers/watchdog/booke_wdt.c b/drivers/watchdog/booke_wdt.c
index a989998..d11ffb0 100644
--- a/drivers/watchdog/booke_wdt.c
+++ b/drivers/watchdog/booke_wdt.c
@@ -33,14 +33,8 @@
  * occur, and the final time the board will reset.
  */
 
-#ifdef	CONFIG_FSL_BOOKE
-#define WDT_PERIOD_DEFAULT 38	/* Ex. wdt_period=28 bus=333Mhz,reset=~40sec */
-#else
-#define WDT_PERIOD_DEFAULT 3	/* Refer to the PPC40x and PPC4xx manuals */
-#endif				/* for timing information */
-
 u32 booke_wdt_enabled;
-u32 booke_wdt_period = WDT_PERIOD_DEFAULT;
+u32 booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;
 
 #ifdef	CONFIG_FSL_BOOKE
 #define WDTP(x)		((((x)&0x3)<<30)|(((x)&0x3c)<<15))