powerpc/8xx: Map IMMR with a huge page

Map the IMMR area with a single 512k huge page.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/9495dba06669da40e133f24607758fa6dcc65f66.1589866984.git.christophe.leroy@csgroup.eu

arch/powerpc/mm/nohash/8xx.c

@@ -118,17 +118,13 @@ static bool immr_is_mapped __initdata;
 
 void __init mmu_mapin_immr(void)
 {
-	unsigned long p = PHYS_IMMR_BASE;
-	unsigned long v = VIRT_IMMR_BASE;
-	int offset;
-
 	if (immr_is_mapped)
 		return;
 
 	immr_is_mapped = true;
 
-	for (offset = 0; offset < IMMR_SIZE; offset += PAGE_SIZE)
-		map_kernel_page(v + offset, p + offset, PAGE_KERNEL_NCG);
+	__early_map_kernel_hugepage(VIRT_IMMR_BASE, PHYS_IMMR_BASE,
+				    PAGE_KERNEL_NCG, MMU_PAGE_512K, true);
 }
 
 unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)