powerpc/mm: remove orphan declarations from mmu_context.h

Remove the following orphan declarations from mmu_context.h:
1. switch_cop() and drop_cop() have been removed since
commit 6ff4d3e9 ("powerpc: Remove old unused icswx
based coprocessor support").

2. mm_iommu_cleanup() has been removed since
commit 4b6fad70 ("powerpc/mm/iommu, vfio/spapr: Put
pages on VFIO container shutdown").

So remove the declarations for them from header file.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220913075029.682327-6-cuigaosheng1@huawei.com

arch/powerpc/include/asm/mmu_context.h

@@ -31,7 +31,6 @@ extern long mm_iommu_newdev(struct mm_struct *mm, unsigned long ua,
 extern long mm_iommu_put(struct mm_struct *mm,
 		struct mm_iommu_table_group_mem_t *mem);
 extern void mm_iommu_init(struct mm_struct *mm);
-extern void mm_iommu_cleanup(struct mm_struct *mm);
 extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
 		unsigned long ua, unsigned long size);
 extern struct mm_iommu_table_group_mem_t *mm_iommu_get(struct mm_struct *mm,
@@ -117,7 +116,6 @@ static inline bool need_extra_context(struct mm_struct *mm, unsigned long ea)
 }
 #endif
 
-extern void switch_cop(struct mm_struct *next);
 extern int use_cop(unsigned long acop, struct mm_struct *mm);
 extern void drop_cop(unsigned long acop, struct mm_struct *mm);