drm: remove usage of drm_pci_alloc/free

Remove usage of legacy dma-api abstraction in preparation for removal

Signed-off-by: Joseph Kogut <joseph.kogut@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210423020248.3427369-1-joseph.kogut@gmail.com