Documentation/printf: struct resource add start == end special case

The code when printing a struct resource will check for start == end and
only print the start value.

Document this special case.

Suggested-by: Petr Mladek <[email protected]>
Signed-off-by: Ira Weiny <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Dave Jiang <[email protected]>

Author: weiny2

Documentation/core-api/printk-formats.rst

@@ -209,12 +209,17 @@ Struct Resources
 ::
 
 	%pr	[mem 0x60000000-0x6fffffff flags 0x2200] or
+		[mem 0x60000000 flags 0x2200] or
 		[mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
+		[mem 0x0000000060000000 flags 0x2200]
 	%pR	[mem 0x60000000-0x6fffffff pref] or
+		[mem 0x60000000 pref] or
 		[mem 0x0000000060000000-0x000000006fffffff pref]
+		[mem 0x0000000060000000 pref]
 
 For printing struct resources. The ``R`` and ``r`` specifiers result in a
-printed resource with (R) or without (r) a decoded flags member.
+printed resource with (R) or without (r) a decoded flags member.  If start is
+equal to end only print the start value.
 
 Passed by reference.