MIPS: check return value of pgtable_pmd_page_ctor

+. According to Documentation/vm/split_page_table_lock, handle failure
of pgtable_pmd_page_ctor

+. Use GFP_KERNEL_ACCOUNT instead of GFP_KERNEL|__GFP_ACCOUNT

+. Adjust coding style

Fixes: ed914d48 ("MIPS: add PMD table accounting into MIPS')
Reported-by: Joshua Kinard <kumba@gentoo.org>
Signed-off-by: Huang Pei <huangpei@loongson.cn>
Reviewed-by: Joshua Kinard <kumba@gentoo.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/include/asm/pgalloc.h

@@ -58,15 +58,20 @@ do {							\
 
 static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
 {
-	pmd_t *pmd = NULL;
+	pmd_t *pmd;
 	struct page *pg;
 
-	pg = alloc_pages(GFP_KERNEL | __GFP_ACCOUNT, PMD_ORDER);
-	if (pg) {
-		pgtable_pmd_page_ctor(pg);
-		pmd = (pmd_t *)page_address(pg);
-		pmd_init((unsigned long)pmd, (unsigned long)invalid_pte_table);
+	pg = alloc_pages(GFP_KERNEL_ACCOUNT, PMD_ORDER);
+	if (!pg)
+		return NULL;
+
+	if (!pgtable_pmd_page_ctor(pg)) {
+		__free_pages(pg, PMD_ORDER);
+		return NULL;
 	}
+
+	pmd = (pmd_t *)page_address(pg);
+	pmd_init((unsigned long)pmd, (unsigned long)invalid_pte_table);
 	return pmd;
 }