linux: Disable GEN_RTC

With CONFIG_GEN_RTC=y set in the defconfig the generic RTC driver will
take precedence over the proper OPAL RTC driver. To the user this
results in errors like:

$ hwclock -r
Sun Dec 31 00:00:00 1899  0.000000 seconds
$ hwclock -w
hwclock: RTC_SET_TIME: Invalid argument

Remove CONFIG_GEN_RTC to allow the OPAL RTC driver to be properly
initialised.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
(cherry picked from commit 9407b0acc8da9b719231d8f305187c307cfd4698)
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/configs/linux/skiroot_defconfig b/openpower/configs/linux/skiroot_defconfig
index d2e60ef..45c40f3 100644
--- a/openpower/configs/linux/skiroot_defconfig
+++ b/openpower/configs/linux/skiroot_defconfig
@@ -155,7 +155,6 @@
 CONFIG_IPMI_DEVICE_INTERFACE=y
 CONFIG_IPMI_POWERNV=y
 CONFIG_HW_RANDOM=y
-CONFIG_GEN_RTC=y
 CONFIG_RAW_DRIVER=y
 CONFIG_MAX_RAW_DEVS=1024
 CONFIG_TCG_TIS_I2C_NUVOTON=y
@@ -184,6 +183,8 @@
 # CONFIG_USB_EHCI_HCD_PPC_OF is not set
 CONFIG_USB_OHCI_HCD=y
 CONFIG_USB_STORAGE=y
+CONFIG_RTC_CLASS=y
+CONFIG_RTC_DRV_GENERIC=m
 CONFIG_VIRT_DRIVERS=y
 CONFIG_VIRTIO_PCI=y
 # CONFIG_IOMMU_SUPPORT is not set