nios2: drop definition of PGD_ORDER

This is the order of the page table allocation, not the order of a PGD. 
Since its always hardwired to 0, simply drop it.

Link: https://lkml.kernel.org/r/20220703141203.147893-9-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Guo Ren <guoren@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Xuerui Wang <kernel@xen0n.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/nios2/include/asm/pgtable.h

@@ -52,9 +52,7 @@ struct mm_struct;
 
 #define PAGE_COPY MKP(0, 0, 1)
 
-#define PGD_ORDER	0
-
-#define PTRS_PER_PGD	((PAGE_SIZE << PGD_ORDER) / sizeof(pgd_t))
+#define PTRS_PER_PGD	(PAGE_SIZE / sizeof(pgd_t))
 #define PTRS_PER_PTE	(PAGE_SIZE / sizeof(pte_t))
 
 #define USER_PTRS_PER_PGD	\