ARM: prima2_defconfig: enable build for RTC

This patch enables RTC_CLASS and RTC driver for SiRFSoC platforms.
Signed-off-by: Barry Song <Baohua.Song@csr.com>

arch/arm/configs/prima2_defconfig

@@ -44,6 +44,8 @@ CONFIG_MMC=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_PLTFM=y
 CONFIG_MMC_SDHCI_SIRF=y
+CONFIG_RTC_CLASS=y
+CONFIG_RTC_DRV_SIRFSOC=y
 CONFIG_DMADEVICES=y
 CONFIG_DMADEVICES_DEBUG=y
 CONFIG_DMADEVICES_VDEBUG=y