rtc: ds1307: Fix wday settings for rx8130

rx8130 wday specifies the bit position, not BCD.

Fixes: ee0981be ("rtc: ds1307: Add support for Epson RX8130CE")
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210420023917.1949066-1-nobuhiro1.iwamatsu@toshiba.co.jp