rtc: pcf85063: scope pcf85063_config structures

Fix possible warning:
>> drivers/rtc/rtc-pcf85063.c:566:37: warning: unused variable 'config_rv8063' [-Wunused-const-variable]
     566 | static const struct pcf85063_config config_rv8063 = {
         |                                     ^~~~~~~~~~~~~

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202507241607.dmz2qrO5-lkp@intel.com/
Link: https://lore.kernel.org/r/20250724090420.917705-1-alexandre.belloni@bootlin.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>