Convert CONFIG_SKIP_LOWLEVEL_INIT et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SKIP_LOWLEVEL_INIT
   CONFIG_SKIP_LOWLEVEL_INIT_ONLY

In order to do this, we need to introduce SPL and TPL variants of these
options so that we can clearly disable these options only in SPL in some
cases, and both instances in other cases.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
index 0863965..dfb63df 100644
--- a/arch/arm/mach-omap2/Kconfig
+++ b/arch/arm/mach-omap2/Kconfig
@@ -120,6 +120,7 @@
 	select SPECIFY_CONSOLE_INDEX
 	imply NAND_OMAP_ELM
 	imply NAND_OMAP_GPMC
+	imply SKIP_LOWLEVEL_INIT
 	imply SPL_NAND_AM33XX_BCH
 	imply SPL_NAND_SUPPORT
 	imply SYS_I2C_OMAP24XX