Convert CONFIG_SPL_INIT_MINIMAL et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_INIT_MINIMAL
   CONFIG_SPL_FLUSH_IMAGE
   CONFIG_SPL_SKIP_RELOCATE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/powerpc/cpu/mpc85xx/cpu_init_early.c b/arch/powerpc/cpu/mpc85xx/cpu_init_early.c
index 5a0d33b..584454e 100644
--- a/arch/powerpc/cpu/mpc85xx/cpu_init_early.c
+++ b/arch/powerpc/cpu/mpc85xx/cpu_init_early.c
@@ -177,7 +177,7 @@
 	invalidate_tlb(1);
 
 #if defined(CONFIG_SYS_PPC_E500_DEBUG_TLB) && \
-	!(defined(CONFIG_SPL_INIT_MINIMAL) && defined(CONFIG_SPL_BUILD)) && \
+	!(CONFIG_IS_ENABLED(INIT_MINIMAL) && defined(CONFIG_SPL_BUILD)) && \
 	!defined(CONFIG_NAND_SPL)
 	disable_tlb(CONFIG_SYS_PPC_E500_DEBUG_TLB);
 #endif