powerpc: opal-core: pair alloc_pages_exact() with free_pages_exact()

opal-core allocates buffers with alloc_pages_exact(), but then
marks them as reserved and frees using free_reserved_area().

This is completely unnecessary and the pages allocated with
alloc_pages_exact() can be naturally freed with free_pages_exact().

Replace freeing of memory in opalcore_cleanup() with
free_pages_exact() and simplify allocation code so that it won't mark
allocated pages as reserved.

Link: https://patch.msgid.link/20260323074836.3653702-4-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

Author: rppt

arch/powerpc/platforms/powernv/opal-core.c

@@ -303,7 +303,6 @@ static int __init create_opalcore(void)
 	struct device_node *dn;
 	struct opalcore *new;
 	loff_t opalcore_off;
-	struct page *page;
 	Elf64_Phdr *phdr;
 	Elf64_Ehdr *elf;
 	int i, ret;
@@ -328,11 +327,6 @@ static int __init create_opalcore(void)
 		oc_conf->opalcorebuf_sz = 0;
 		return -ENOMEM;
 	}
-	count = oc_conf->opalcorebuf_sz / PAGE_SIZE;
-	page = virt_to_page(oc_conf->opalcorebuf);
-	for (i = 0; i < count; i++)
-		mark_page_reserved(page + i);
-
 	pr_debug("opalcorebuf = 0x%llx\n", (u64)oc_conf->opalcorebuf);
 
 	/* Read OPAL related device-tree entries */
@@ -437,10 +431,7 @@ static void opalcore_cleanup(void)
 
 	/* free the buffer used for setting up OPAL core */
 	if (oc_conf->opalcorebuf) {
-		void *end = (void *)((u64)oc_conf->opalcorebuf +
-				     oc_conf->opalcorebuf_sz);
-
-		free_reserved_area(oc_conf->opalcorebuf, end, -1, NULL);
+		free_pages_exact(oc_conf->opalcorebuf, oc_conf->opalcorebuf_sz);
 		oc_conf->opalcorebuf = NULL;
 		oc_conf->opalcorebuf_sz = 0;
 	}