drm/shmem-helper: Remove obsoleted is_iomem test

drm/shmem-helper: Remove obsoleted is_iomem test

commit eab10538073c3ff9e21c857bd462f79f2f6f7e00 upstream.

Everything that uses the mapped buffer should be agnostic to is_iomem.
The only reason for the is_iomem test is that we're setting shmem->vaddr
to the returned map->vaddr. Now that the shmem->vaddr code is gone, remove
the obsoleted is_iomem test to clean up the code.

Acked-by: Maxime Ripard <mripard@kernel.org>
Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.d>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250322212608.40511-7-dmitry.osipenko@collabora.com
Stable-dep-of: 6d496e956998 ("Revert "drm/gem-shmem: Use dma_buf from GEM object instance"")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>