mm: always define pxx_pgprot()

There're:

  - 8 archs (arc, arm64, include, mips, powerpc, s390, sh, x86) that
  support pte_pgprot().

  - 2 archs (x86, sparc) that support pmd_pgprot().

  - 1 arch (x86) that support pud_pgprot().

Always define them to be used in generic code, and then we don't need to
fiddle with "#ifdef"s when doing so.

Link: https://lkml.kernel.org/r/20240826204353.2228736-9-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/pgtable.h

@@ -1956,6 +1956,18 @@ typedef unsigned int pgtbl_mod_mask;
 #define MAX_PTRS_PER_P4D PTRS_PER_P4D
 #endif
 
+#ifndef pte_pgprot
+#define pte_pgprot(x) ((pgprot_t) {0})
+#endif
+
+#ifndef pmd_pgprot
+#define pmd_pgprot(x) ((pgprot_t) {0})
+#endif
+
+#ifndef pud_pgprot
+#define pud_pgprot(x) ((pgprot_t) {0})
+#endif
+
 /* description of effects of mapping type and prot in current implementation.
  * this is due to the limited x86 page protection hardware.  The expected
  * behavior is in parens: