powerpc: Remove warm reset entry point

No boards utilize the warm reset entry point, so remove it.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/arch/powerpc/cpu/mpc85xx/start.S b/arch/powerpc/cpu/mpc85xx/start.S
index 3278b10..91096ad 100644
--- a/arch/powerpc/cpu/mpc85xx/start.S
+++ b/arch/powerpc/cpu/mpc85xx/start.S
@@ -432,6 +432,8 @@
 	bl	board_init_f
 	isync
 
+	/* NOTREACHED - board_init_f() does not return */
+
 #ifndef CONFIG_NAND_SPL
 	. = EXC_OFF_SYS_RESET
 	.globl	_start_of_vectors