watchdog: update/improve/consolidate watchdog driver

Move the limited watchdog driver help from kernel-parameters.txt
to Documentation/watchdog/watchdog-parameters.txt and add info to it
for all watchdog drivers except the ones that have driver-specific
files already.

Correct minor comments and MODULE_PARM_DESC() text in 2 places.

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

diff --git a/drivers/watchdog/wdt.c b/drivers/watchdog/wdt.c
index bfda2e9..552a438 100644
--- a/drivers/watchdog/wdt.c
+++ b/drivers/watchdog/wdt.c
@@ -91,7 +91,7 @@
 static int type = 500;
 module_param(type, int, 0);
 MODULE_PARM_DESC(type,
-		"WDT501-P Card type (500 or 501 , default=500)");
+		"WDT501-P Card type (500 or 501, default=500)");
 
 /*
  *	Programming support