mm: introduce pte_advance_pfn() and use for pte_next_pfn()

The goal is to be able to advance a PTE by an arbitrary number of PFNs. 
So introduce a new API that takes a nr param.  Define the default
implementation here and allow for architectures to override. 
pte_next_pfn() becomes a wrapper around pte_advance_pfn().

Follow up commits will convert each overriding architecture's
pte_next_pfn() to pte_advance_pfn().

Link: https://lkml.kernel.org/r/20240215103205.2607016-4-ryan.roberts@arm.comSigned-off-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Morse <james.morse@arm.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/pgtable.h

@@ -212,14 +212,17 @@ static inline int pmd_dirty(pmd_t pmd)
 #define arch_flush_lazy_mmu_mode()	do {} while (0)
 #endif
 
-
 #ifndef pte_next_pfn
-static inline pte_t pte_next_pfn(pte_t pte)
+#ifndef pte_advance_pfn
+static inline pte_t pte_advance_pfn(pte_t pte, unsigned long nr)
 {
-	return __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
+	return __pte(pte_val(pte) + (nr << PFN_PTE_SHIFT));
 }
 #endif
 
+#define pte_next_pfn(pte) pte_advance_pfn(pte, 1)
+#endif
+
 #ifndef set_ptes
 /**
  * set_ptes - Map consecutive pages to a contiguous range of addresses.