[ppc4xx] Fix problem with NAND booting on AMCC Acadia

The latest changes showed a problem with the location of the NAND-SPL
image in the OCM and the init-data area (incl. cache). This patch
fixes this problem.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/board/amcc/acadia/acadia.c b/board/amcc/acadia/acadia.c
index 46d63e6..0f54025 100644
--- a/board/amcc/acadia/acadia.c
+++ b/board/amcc/acadia/acadia.c
@@ -55,10 +55,12 @@
 {
 	unsigned int reg;
 
+#if !defined(CONFIG_NAND_U_BOOT)
 	/* don't reinit PLL when booting via I2C bootstrap option */
 	mfsdr(SDR_PINSTP, reg);
 	if (reg != 0xf0000000)
 		board_pll_init_f();
+#endif
 
 	acadia_gpio_init();