sparc32: use PUD rather than PGD to get PMD in srmmu_nocache_init()

The kbuild test robot reported the following warning:

arch/sparc/mm/srmmu.c: In function 'srmmu_nocache_init': arch/sparc/mm/srmmu.c:300:9: error: variable 'pud' set but not used [-Werror=unused-but-set-variable]
300 | pud_t *pud;

This warning is caused by misprint in the page table traversal in
srmmu_nocache_init() function which accessed a PMD entry using PGD
rather than PUD.

Since sparc32 has only 3 page table levels, the PGD and PUD are
essentially the same and usage of __nocache_fix() removed the type
checking.

Use PUD for the consistency and to silence the compiler warning.

Fixes: 7235db268a2777bc38 ("sparc32: use pgtable-nopud instead of 4level-fixup")
Reported-by: kbuild test robot <[e-mail]>
Signed-off-by: Mike Rapoport <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Anatoly Pugachev <[e-mail]>
Cc: <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

arch/sparc/mm/srmmu.c

···
 		pgd = pgd_offset_k(vaddr);
 		p4d = p4d_offset(__nocache_fix(pgd), vaddr);
 		pud = pud_offset(__nocache_fix(p4d), vaddr);
-		pmd = pmd_offset(__nocache_fix(pgd), vaddr);
+		pmd = pmd_offset(__nocache_fix(pud), vaddr);
 		pte = pte_offset_kernel(__nocache_fix(pmd), vaddr);
 
 		pteval = ((paddr >> 4) | SRMMU_ET_PTE | SRMMU_PRIV);