mips: rename PGD_ORDER to PGD_TABLE_ORDER

mips: rename PGD_ORDER to PGD_TABLE_ORDER

This is the order of the page table allocation, not the order of a PGD.

While at it remove unused defintion of _PGD_ORDER in asm-offsets.

Link: https://lkml.kernel.org/r/20220703141203.147893-7-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dinh Nguyen <dinguyen@kernel.org>
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>