drm/ttm: remove comment referencing now-removed vmf_insert_mixed_prot()

This function no longer exists, however the prot != vma->vm_page_prot case
discussion has been retained and moved to vmf_insert_pfn_prot() so refer
to this instead.

Link: https://lkml.kernel.org/r/db403b3622b94a87bd93528cc1d6b44ae88adcdd.1678661628.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Aaron Tomlin <atomlin@atomlin.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/gpu/drm/ttm/ttm_bo_vm.c

@@ -254,7 +254,7 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
 		 * encryption bits. This is because the exact location of the
 		 * data may not be known at mmap() time and may also change
 		 * at arbitrary times while the data is mmap'ed.
-		 * See vmf_insert_mixed_prot() for a discussion.
+		 * See vmf_insert_pfn_prot() for a discussion.
 		 */
 		ret = vmf_insert_pfn_prot(vma, address, pfn, prot);