dt-bindings: rtc: Add Epson RX8111

Epson RX8111 is an RTC with timestamp functionality. Add devicetree
bindings requiring the compatible string and I2C slave address (reg)
through `trivial-rtc.yaml`.

Acked-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Waqar Hameed <[e-mail]>
Link: https://lore.kernel.org/r/4823[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

Documentation/devicetree/bindings/rtc/trivial-rtc.yaml

···
       - epson,rx8025
       - epson,rx8035
       # I2C-BUS INTERFACE REAL TIME CLOCK MODULE with Battery Backed RAM
+      - epson,rx8111
       - epson,rx8571
       # I2C-BUS INTERFACE REAL TIME CLOCK MODULE
       - epson,rx8581