lib/vsprintf.c: document more vsnprintf extensions

These were added in

9ac6e44e (lib/vsprintf.c: add %pU to print UUID/GUIDs)
c7dabef8 (vsprintf: use %pR, %pr instead of %pRt, %pRf)
8a27f7c9 (lib/vsprintf.c: Add "%pI6c" - print pointer as compressed ipv6 address)
4aa99606 (printk: add %I4, %I6, %i4, %i6 format specifiers)
dd45c9cf (printk: add %pM format specifier for MAC addresses)

but only added comments to pointer() not vsnprintf() that is refered to by
printk's comments.
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Harvey Harrison <harvey.harrison@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Joe Perches <joe@perches.com>
Cc: Jens Rosenboom <jens@mcbone.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lib/vsprintf.c

@@ -1179,7 +1179,18 @@ static int format_decode(const char *fmt, struct printf_spec *spec)
  * %ps output the name of a text symbol without offset
  * %pF output the name of a function pointer with its offset
  * %pf output the name of a function pointer without its offset
- * %pR output the address range in a struct resource
+ * %pR output the address range in a struct resource with decoded flags
+ * %pr output the address range in a struct resource with raw flags
+ * %pM output a 6-byte MAC address with colons
+ * %pm output a 6-byte MAC address without colons
+ * %pI4 print an IPv4 address without leading zeros
+ * %pi4 print an IPv4 address with leading zeros
+ * %pI6 print an IPv6 address with colons
+ * %pi6 print an IPv6 address without colons
+ * %pI6c print an IPv6 address as specified by
+ *   http://www.ietf.org/id/draft-kawamura-ipv6-text-representation-03.txt
+ * %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper
+ *   case.
  * %n is ignored
  *
  * The return value is the number of characters which would