powerpc: Remove stale declarations in mmu_decl.h

rtas_size and rtas_data are not used anymore since at least
commit 7c8c6b97 ("powerpc: Merge lmb.c and make MM initialization
use it.")

Remove them.

Since commit 4b74a35f ("powerpc/32s: Make Hash var static")
the forward declaration of struct hash_pte is unneeded.

Remove it.

__initial_memory_limit_addr was removed by commit e63075a3 ("memblock:
Introduce default allocation limit and use it to replace explicit ones")

Remove the declaration.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a821e8397dd56b8177ecc04966d3b3a7c4bda6d4.1660919016.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/setup.h

@@ -7,7 +7,6 @@
 #ifndef __ASSEMBLY__
 extern void ppc_printk_progress(char *s, unsigned short hex);
 
-extern unsigned int rtas_data;
 extern unsigned long long memory_limit;
 extern void *zalloc_maybe_bootmem(size_t size, gfp_t mask);
 

arch/powerpc/mm/mmu_decl.h

@@ -92,15 +92,11 @@ extern void mapin_ram(void);
 extern void setbat(int index, unsigned long virt, phys_addr_t phys,
 		   unsigned int size, pgprot_t prot);
 
-extern unsigned int rtas_data, rtas_size;
-
-struct hash_pte;
 extern u8 early_hash[];
 
 #endif /* CONFIG_PPC32 */
 
 extern unsigned long __max_low_memory;
-extern phys_addr_t __initial_memory_limit_addr;
 extern phys_addr_t total_memory;
 extern phys_addr_t total_lowmem;
 extern phys_addr_t memstart_addr;