dma-buf-map: remove renamed header file

commit 7938f421 ("dma-buf-map: Rename to iosys-map") already renamed
this file, but it got brought back by a merge.

Delete it for real this time.

Fixes: 30424eba

 ("Merge tag 'drm-intel-gt-next-2022-02-17' of git://anongit.freedesktop.org/drm/drm-intel into drm-intel-next")
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220411134404.524776-1-kherbst@redhat.com