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/am43xx_evm_rtconly_defconfig b/configs/am43xx_evm_rtconly_defconfig
index ebe65f9..bf881ac 100644
--- a/configs/am43xx_evm_rtconly_defconfig
+++ b/configs/am43xx_evm_rtconly_defconfig
@@ -11,6 +11,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="CONS_INDEX=1"
 # CONFIG_USE_BOOTCOMMAND is not set
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
+# CONFIG_MISC_INIT_R is not set
 CONFIG_VERSION_VARIABLE=y
 CONFIG_SPL_MTD_SUPPORT=y
 CONFIG_SPL_OS_BOOT=y