Convert CONFIG_SUPPORT_EMMC_RPMB to Kconfig

This converts the following to Kconfig:
   CONFIG_SUPPORT_EMMC_RPMB

This fixes a few platforms where the option was not taking effect as
intended.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/evb-rk3308_defconfig b/configs/evb-rk3308_defconfig
index 3194a2b..a3a319f 100644
--- a/configs/evb-rk3308_defconfig
+++ b/configs/evb-rk3308_defconfig
@@ -49,6 +49,7 @@
 # CONFIG_USB_FUNCTION_FASTBOOT is not set
 CONFIG_ROCKCHIP_GPIO=y
 CONFIG_SYS_I2C_ROCKCHIP=y
+CONFIG_SUPPORT_EMMC_RPMB=y
 CONFIG_MMC_DW=y
 CONFIG_MMC_DW_ROCKCHIP=y
 CONFIG_DM_ETH=y