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/tlb.c b/arch/powerpc/cpu/mpc85xx/tlb.c
index 550d45d..4f6778c 100644
--- a/arch/powerpc/cpu/mpc85xx/tlb.c
+++ b/arch/powerpc/cpu/mpc85xx/tlb.c
@@ -44,7 +44,7 @@
 }
 
 #if !defined(CONFIG_NAND_SPL) && \
-	(!defined(CONFIG_SPL_BUILD) || !defined(CONFIG_SPL_INIT_MINIMAL))
+	(!defined(CONFIG_SPL_BUILD) || !CONFIG_IS_ENABLED(INIT_MINIMAL))
 void read_tlbcam_entry(int idx, u32 *valid, u32 *tsize, unsigned long *epn,
 		       phys_addr_t *rpn)
 {