powerpc/85xx/defconfig: Remove duplicate CONFIG_RTC_DRV_DS1307

Commit a95e8c28 "powerpc/defconfig: update RTC support" duplicated
the CONFIG_RTC_DRV_DS1307 symbol in mpc85xx_defconfig and
mpc85xx_smp_defconfig, resulting in this:

arch/powerpc/configs/mpc85xx_smp_defconfig:217:warning: override: reassigning to symbol RTC_DRV_DS1307

Fixes: a95e8c28 "powerpc/defconfig: update RTC support"
Cc: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/configs/mpc85xx_defconfig

@@ -213,7 +213,6 @@ CONFIG_RTC_DRV_DS1307=y
 CONFIG_RTC_DRV_DS1374=y
 CONFIG_RTC_DRV_DS3232=y
 CONFIG_RTC_DRV_CMOS=y
-CONFIG_RTC_DRV_DS1307=y
 CONFIG_DMADEVICES=y
 CONFIG_FSL_DMA=y
 # CONFIG_NET_DMA is not set

arch/powerpc/configs/mpc85xx_smp_defconfig

@@ -214,7 +214,6 @@ CONFIG_RTC_DRV_DS1307=y
 CONFIG_RTC_DRV_DS1374=y
 CONFIG_RTC_DRV_DS3232=y
 CONFIG_RTC_DRV_CMOS=y
-CONFIG_RTC_DRV_DS1307=y
 CONFIG_DMADEVICES=y
 CONFIG_FSL_DMA=y
 # CONFIG_NET_DMA is not set