MIPS: Fix 64k page support for 32 bit kernels.

TASK_SIZE was defined as 0x7fff8000UL which for 64k pages is not a
multiple of the page size.  Somewhere further down the math fails
such that executing an ELF binary fails.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
Tested-by: NJoshua Henderson <joshua.henderson@microchip.com>

arch/mips/include/asm/processor.h

@@ -45,7 +45,7 @@ extern unsigned int vced_count, vcei_count;
  * User space process size: 2GB. This is hardcoded into a few places,
  * so don't change it unless you know what you are doing.
  */
-#define TASK_SIZE	0x7fff8000UL
+#define TASK_SIZE	0x80000000UL
 #endif
 
 #define STACK_TOP_MAX	TASK_SIZE