powerpc/mpc5200: Disable bestcomm prefetching when ATA DMA enabled

When ATA DMA is enabled, bestcomm prefetching does not work.  This
patch adds a function to disable bestcomm prefetch when the ATA
Bestcomm task is initialized.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/arch/powerpc/sysdev/bestcomm/bestcomm.c b/arch/powerpc/sysdev/bestcomm/bestcomm.c
index 446c9ea..378ebd9 100644
--- a/arch/powerpc/sysdev/bestcomm/bestcomm.c
+++ b/arch/powerpc/sysdev/bestcomm/bestcomm.c
@@ -279,7 +279,6 @@
 	int task;
 	phys_addr_t tdt_pa, ctx_pa, var_pa, fdt_pa;
 	unsigned int tdt_size, ctx_size, var_size, fdt_size;
-	u16 regval;
 
 	/* Allocate & clear SRAM zones for FDT, TDTs, contexts and vars/incs */
 	tdt_size = BCOM_MAX_TASKS * sizeof(struct bcom_tdt);
@@ -331,10 +330,8 @@
 	out_8(&bcom_eng->regs->ipr[BCOM_INITIATOR_ALWAYS], BCOM_IPR_ALWAYS);
 
 	/* Disable COMM Bus Prefetch on the original 5200; it's broken */
-	if ((mfspr(SPRN_SVR) & MPC5200_SVR_MASK) == MPC5200_SVR) {
-		regval = in_be16(&bcom_eng->regs->PtdCntrl);
-		out_be16(&bcom_eng->regs->PtdCntrl,  regval | 1);
-	}
+	if ((mfspr(SPRN_SVR) & MPC5200_SVR_MASK) == MPC5200_SVR)
+		bcom_disable_prefetch();
 
 	/* Init lock */
 	spin_lock_init(&bcom_eng->lock);