rtc: pcf2123: Fix build error

If REGMAP_SPI is m and RTC_DRV_PCF2123 is y,

drivers/rtc/rtc-pcf2123.o: In function `pcf2123_probe':
rtc-pcf2123.c:(.text+0xb2b): undefined reference to `__devm_regmap_init_spi'

Select REGMAP_SPI as RTC_DRV_DS1347 driver does.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 790d0339

 ("rtc: pcf2123: port to regmap")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190704085542.48180-1-yuehaibing@huawei.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>