lib/vsprintf: Print time and date in human readable format via %pt

lib/vsprintf: Print time and date in human readable format via %pt

There are users which print time and date represented by content of
struct rtc_time in human readable format.

Instead of open coding that each time introduce %ptR[dt][r] specifier.

Cc: Arnd Bergmann <[email protected]>
Cc: Bartlomiej Zolnierkiewicz <[email protected]>
Cc: Dmitry Torokhov <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Wessel <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Jonathan Hunter <[email protected]>
Cc: Krzysztof Kozlowski <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Petr Mladek <[email protected]>
Signed-off-by: Andy Shevchenko <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Signed-off-by: Alexandre Belloni <[email protected]>