MIPS: Calculate proper ebase value for 64-bit kernels

The ebase is relative to CKSEG0 not CAC_BASE.  On a 32-bit kernel they
are the same thing, for a 64-bit kernel they are not.

It happens to kind of work on a 64-bit kernel as they both reference
the same physical memory.  However since the CPU uses the CKSEG0 base,
determining if a J instruction will reach always gives the wrong result
unless we use the same number the CPU uses.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/1093/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/traps.c

@@ -1599,7 +1599,7 @@ void __init trap_init(void)
 		ebase = (unsigned long)
 			__alloc_bootmem(size, 1 << fls(size), 0);
 	} else {
-		ebase = CAC_BASE;
+		ebase = CKSEG0;
 		if (cpu_has_mips_r2)
 			ebase += (read_c0_ebase() & 0x3ffff000);
 	}