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_ethboot_defconfig b/configs/am43xx_evm_ethboot_defconfig
index 9463817..4c953e9 100644
--- a/configs/am43xx_evm_ethboot_defconfig
+++ b/configs/am43xx_evm_ethboot_defconfig
@@ -6,6 +6,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="SERIAL1,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_SYS_MALLOC_SIMPLE is not set
 CONFIG_SPL_ETH_SUPPORT=y