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 <pmladek@suse.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20241025-cxl-pra-v2-2-123a825daba2@intel.com


Signed-off-by: Dave Jiang <dave.jiang@intel.com>