powerpc/mm: Remove stale do_page_fault comment referring to SLB faults

SLB faults no longer call do_page_fault, this was removed somewhere
between 2.6.0 and 2.6.12.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210130130852.2952424-17-npiggin@gmail.com

arch/powerpc/mm/fault.c

@@ -377,13 +377,11 @@ static void sanity_check_fault(bool is_write, bool is_user,
 
 /*
  * For 600- and 800-family processors, the error_code parameter is DSISR
- * for a data fault, SRR1 for an instruction fault. For 400-family processors
- * the error_code parameter is ESR for a data fault, 0 for an instruction
- * fault.
- * For 64-bit processors, the error_code parameter is
- *  - DSISR for a non-SLB data access fault,
- *  - SRR1 & 0x08000000 for a non-SLB instruction access fault
- *  - 0 any SLB fault.
+ * for a data fault, SRR1 for an instruction fault.
+ * For 400-family processors the error_code parameter is ESR for a data fault,
+ * 0 for an instruction fault.
+ * For 64-bit processors, the error_code parameter is DSISR for a data access
+ * fault, SRR1 & 0x08000000 for an instruction access fault.
  *
  * The return value is 0 if the fault was handled, or the signal
  * number if this is a kernel fault that can't be handled here.