board_r: fix build with DM_SPI

CC      common/board_r.o
common/board_r.c:747:2: error: ‘initr_spi’ undeclared here (not in a function)
  initr_spi,
  ^
make[1]: *** [common/board_r.o] Error 1

Fixes: ebe76a2d ("dm: Remove spi_init() from board_r.c when using driver model")
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>

common/board_r.c

@@ -743,7 +743,7 @@ static init_fnc_t init_sequence_r[] = {
 	/* initialize higher level parts of CPU like time base and timers */
 	cpu_init_r,
 #endif
-#ifdef CONFIG_PPC
+#if defined(CONFIG_PPC) && !defined(CONFIG_DM_SPI)
 	initr_spi,
 #endif
 #ifdef CONFIG_CMD_NAND