Convert CONFIG_SYS_MPC85XX_NO_RESETVEC to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MPC85XX_NO_RESETVEC

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/powerpc/cpu/mpc85xx/u-boot.lds b/arch/powerpc/cpu/mpc85xx/u-boot.lds
index 4e137e0..8fba712 100644
--- a/arch/powerpc/cpu/mpc85xx/u-boot.lds
+++ b/arch/powerpc/cpu/mpc85xx/u-boot.lds
@@ -19,7 +19,7 @@
   /* Read-only sections, merged into text segment: */
   .text      :
   {
-#ifdef CONFIG_SYS_MPC85XX_NO_RESETVEC
+#if CONFIG_IS_ENABLED(SYS_MPC85XX_NO_RESETVEC)
     KEEP(arch/powerpc/cpu/mpc85xx/start.o (.bootpg))
 #endif
     *(.text*)
@@ -74,7 +74,7 @@
   __init_end = .;
   _end = .;
 
-#ifndef CONFIG_SYS_MPC85XX_NO_RESETVEC
+#if !CONFIG_IS_ENABLED(SYS_MPC85XX_NO_RESETVEC)
   .bootpg RESET_VECTOR_ADDRESS - 0xffc :
   {
     arch/powerpc/cpu/mpc85xx/start.o	(.bootpg)