Use %ptR instead of open coded variant to print content of
struct rtc_time in human readable format.

Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>