[PATCH -next] arm64: fix -Wundef warning for PUD_SHIFT

[Zhang Jianhua]

When building with W=1, the following warning occurs.

arch/arm64/include/asm/kernel-pgtable.h:129:41: error: "PUD_SHIFT" is not defined, evaluates to 0 [-Werror=undef]
  129 | #define ARM64_MEMSTART_SHIFT            PUD_SHIFT
      |                                         ^~~~~~~~~
arch/arm64/include/asm/kernel-pgtable.h:142:5: note: in expansion of macro ‘ARM64_MEMSTART_SHIFT’
  142 | #if ARM64_MEMSTART_SHIFT < SECTION_SIZE_BITS
      |     ^~~~~~~~~~~~~~~~~~~~

The reason is that PUD_SHIFT isn't defined if CONFIG_PGTABLE_LEVELS ==
3, and at this time PUD_SHIFT is equal to PGDIR_SHIFT, so define it.

Fixes: 06e9bf2fd9b3 ("arm64: choose memstart_addr based on minimum sparsemem section alignment")
Signed-off-by: Zhang Jianhua <chris.zjh@xxxxxxxxxx>
---
v2:
	Define PUD_SHIFT before use it instead of judgement
---
---
 arch/arm64/include/asm/kernel-pgtable.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 577773870b66..996a144e2929 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -59,6 +59,10 @@
 #define EARLY_KASLR	(0)
 #endif
 
+#ifndef PUD_SHIFT
+#define PUD_SHIFT PGDIR_SHIFT
+#endif
+
 #define SPAN_NR_ENTRIES(vstart, vend, shift) \
 	((((vend) - 1) >> (shift)) - ((vstart) >> (shift)) + 1)
 
-- 
2.34.1