mips: bmips: BCM6358: make sure CBR is correctly set

It was discovered that some device have CBR address set to 0 causing
kernel panic when arch_sync_dma_for_cpu_all is called.

This was notice in situation where the system is booted from TP1 and
BMIPS_GET_CBR() returns 0 instead of a valid address and
!!(read_c0_brcm_cmt_local() & (1 << 31)); not failing.

The current check whether RAC flush should be disabled or not are not
enough hence lets check if CBR is a valid address or not.

Fixes: ab327f8a ("mips: bmips: BCM6358: disable RAC flush for TP1")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/bmips/setup.c

@@ -110,7 +110,8 @@ static void bcm6358_quirks(void)
 	 * RAC flush causes kernel panics on BCM6358 when booting from TP1
 	 * because the bootloader is not initializing it properly.
 	 */
-	bmips_rac_flush_disable = !!(read_c0_brcm_cmt_local() & (1 << 31));
+	bmips_rac_flush_disable = !!(read_c0_brcm_cmt_local() & (1 << 31)) ||
+				  !!BMIPS_GET_CBR();
 }
 
 static void bcm6368_quirks(void)