drm: remove pgprot_decrypted() before calls to io_remap_pfn_range()

commit f8f6ae5d ("mm: always have io_remap_pfn_range() set
pgprot_decrypted()") moves the pgprot_decrypted() into
io_remap_pfn_range(). Delete any, now confusing, open coded calls that
directly precede io_remap_pfn_range():

- drm_io_prot() is only in drm_mmap_locked() to call io_remap_pfn_range()

- fb_mmap() immediately calls vm_iomap_memory() which is a convenience
  wrapper for io_remap_pfn_range()

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/0-v1-2e6a0db57868+166-drm_sme_clean_jgg@nvidia.com