pps: Open writable renderer node in DrmDevice::create

pps: Open writable renderer node in DrmDevice::create

DrmDevice::create_all correctly opened the node with O_RDWR, while
DrmDevice::create was not, causing failure to create writable buffer.

Fixes pps-config on Freedreno.

Fixes: 1cc72b2aef82373247466c2e7b81970c867ad0fa
("pps: Gfx-pps v0.3.0")

Signed-off-by: Danylo Piliaiev <dpiliaiev@igalia.com>
Reviewed-by: Antonio Caggiano <antonio.caggiano@collabora.com>
Reviewed-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16406>