powerpc/ps3: replace __ioremap() by ioremap_prot()

__ioremap() is similar to ioremap_prot() except that ioremap_prot()
does a few sanity changes in addition.

The flags used by PS3 are not impacted by those changes so for
PS3 both functions are equivalent.

At the same time, drop parts of the comment that have been invalid
since commit e58e87ad ("powerpc/mm: Update _PAGE_KERNEL_RO")
Suggested-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/36bff5d875ff562889c5e12dab63e5d7c5d1fbd8.1566309262.git.christophe.leroy@c-s.fr

arch/powerpc/platforms/ps3/spu.c

@@ -184,10 +184,7 @@ static void spu_unmap(struct spu *spu)
  * setup_areas - Map the spu regions into the address space.
  *
  * The current HV requires the spu shadow regs to be mapped with the
- * PTE page protection bits set as read-only (PP=3).  This implementation
- * uses the low level __ioremap() to bypass the page protection settings
- * inforced by ioremap_prot() to get the needed PTE bits set for the
- * shadow regs.
+ * PTE page protection bits set as read-only.
  */
 
 static int __init setup_areas(struct spu *spu)
@@ -195,9 +192,8 @@ static int __init setup_areas(struct spu *spu)
 	struct table {char* name; unsigned long addr; unsigned long size;};
 	unsigned long shadow_flags = pgprot_val(pgprot_noncached_wc(PAGE_KERNEL_RO));
 
-	spu_pdata(spu)->shadow = __ioremap(spu_pdata(spu)->shadow_addr,
-					   sizeof(struct spe_shadow),
-					   shadow_flags);
+	spu_pdata(spu)->shadow = ioremap_prot(spu_pdata(spu)->shadow_addr,
+					      sizeof(struct spe_shadow), shadow_flags);
 	if (!spu_pdata(spu)->shadow) {
 		pr_debug("%s:%d: ioremap shadow failed\n", __func__, __LINE__);
 		goto fail_ioremap;