Convert CONFIG_MISC_INIT_R to Kconfig

This converts the following to Kconfig:
   CONFIG_MISC_INIT_R

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Update the defaults logic slightly]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig b/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig
index 828aae4..fa40cc4 100644
--- a/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig
+++ b/configs/P2020RDB-PC_36BIT_SPIFLASH_defconfig
@@ -16,6 +16,7 @@
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_SYS_EXTRA_OPTIONS="SPIFLASH"
 CONFIG_BOOTDELAY=10
+# CONFIG_MISC_INIT_R is not set
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_BOARD_EARLY_INIT_R=y
 # CONFIG_SPL_FRAMEWORK is not set