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/cpu/arm920t/start.S b/arch/arm/cpu/arm920t/start.S
index e2b5f2b..02cbda9 100644
--- a/arch/arm/cpu/arm920t/start.S
+++ b/arch/arm/cpu/arm920t/start.S
@@ -53,7 +53,7 @@
 	 * we do sys-critical inits only at reboot,
 	 * not when booting from ram!
 	 */
-#ifndef CONFIG_SKIP_LOWLEVEL_INIT
+#if !CONFIG_IS_ENABLED(SKIP_LOWLEVEL_INIT)
 	bl	cpu_init_crit
 #endif
 
@@ -78,7 +78,7 @@
  */
 
 
-#ifndef CONFIG_SKIP_LOWLEVEL_INIT
+#if !CONFIG_IS_ENABLED(SKIP_LOWLEVEL_INIT)
 cpu_init_crit:
 	/*
 	 * flush v4 I/D caches
@@ -97,7 +97,7 @@
 	orr	r0, r0, #0x00001000	@ set bit 12 (I) I-Cache
 	mcr	p15, 0, r0, c1, c0, 0
 
-#ifndef CONFIG_SKIP_LOWLEVEL_INIT_ONLY
+#if !CONFIG_IS_ENABLED(SKIP_LOWLEVEL_INIT_ONLY)
 	/*
 	 * before relocating, we have to setup RAM timing
 	 * because memory timing is board-dependend, you will
@@ -109,4 +109,4 @@
 	mov	lr, ip
 #endif
 	mov	pc, lr
-#endif /* CONFIG_SKIP_LOWLEVEL_INIT */
+#endif /* CONFIG_IS_ENABLED(SKIP_LOWLEVEL_INIT) */