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

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: ff4daf22041b5ce4a6 ("sparc32: use pgtable-nopud instead of 4level-fixup")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Anatoly Pugachev <matorola@gmail.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200520132005.GM1059226@linux.ibm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>