s390/mm: Remove incorrect comment

Remove an outdated comment that is also located at a random place. The
generic statement that read permissions imply execute permissions is
wrong since the instruction execution-protection facility is available.

Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Author: hcahca

arch/s390/include/asm/pgtable.h

@@ -461,13 +461,6 @@ static inline int is_module_addr(void *addr)
 #define PAGE_KERNEL_EXEC __pgprot(_PAGE_PRESENT | _PAGE_READ | _PAGE_WRITE | \
 				  _PAGE_YOUNG |	_PAGE_DIRTY)
 
-/*
- * On s390 the page table entry has an invalid bit and a read-only bit.
- * Read permission implies execute permission and write permission
- * implies read permission.
- */
-         /*xwr*/
-
 /*
  * Segment entry (large page) protection definitions.
  */