We now support TASK_SIZE of 16TB, hence the array should be 8.
Fixes the below crash:
Unable to handle kernel paging request for data at address 0x000100bd
Faulting instruction address: 0xc00000000004f914
cpu 0x13: Vector: 300 (Data Access) at [
c000000fea75fa90]
    pc: 
c00000000004f914: .sys_subpage_prot+0x2d4/0x5c0
    lr: 
c00000000004fb5c: .sys_subpage_prot+0x51c/0x5c0
    sp: 
c000000fea75fd10
   msr: 
9000000000009032
   dar: 100bd
 dsisr: 
40000000
  current = 0xc000000fea6ae490
  paca    = 0xc00000000fb8ab00   softe: 0        irq_happened: 0x00
    pid   = 8237, comm = a.out
enter ? for help
[
c000000fea75fe30] 
c00000000000a164 syscall_exit+0x0/0x98
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
 
  */
 #include <asm/pgtable-ppc64.h>
 #include <asm/bug.h>
+#include <asm/processor.h>
 
 /*
  * Segment table
  */
 struct subpage_prot_table {
        unsigned long maxaddr;  /* only addresses < this are protected */
-       unsigned int **protptrs[2];
+       unsigned int **protptrs[(TASK_SIZE_USER64 >> 43)];
        unsigned int *low_prot[4];
 };