drm/rockchip: dsi: Hold pm-runtime across bind/unbind

drm/rockchip: dsi: Hold pm-runtime across bind/unbind

In commit 43c2de1002d2 ("drm/rockchip: dsi: move all lane config except
LCDC mux to bind()"), we moved most HW configuration to bind(), but we
didn't move the runtime PM management. Therefore, depending on initial
boot state, runtime-PM workqueue delays, and other timing factors, we
may disable our power domain in between the hardware configuration
(bind()) and when we enable the display. This can cause us to lose
hardware state and fail to configure our display. For example:

  dw-mipi-dsi-rockchip ff968000.mipi: failed to write command FIFO
  panel-innolux-p079zca ff960000.mipi.0: failed to write command 0

or:

  dw-mipi-dsi-rockchip ff968000.mipi: failed to write command FIFO
  panel-kingdisplay-kd097d04 ff960000.mipi.0: failed write init cmds: -110

We should match the runtime PM to the lifetime of the bind()/unbind()
cycle.

Tested on Acer Chrometab 10 (RK3399 Gru-Scarlet), with panel drivers
built either as modules or built-in.

Side notes: it seems one is more likely to see this problem when the
panel driver is built into the kernel. I've also seen this problem
bisect down to commits that simply changed Kconfig dependencies, because
it changed the order in which driver init functions were compiled into
the kernel, and therefore the ordering and timing of built-in device
probe.

Fixes: 43c2de1002d2 ("drm/rockchip: dsi: move all lane config except LCDC mux to bind()")
Link: https://lore.kernel.org/linux-rockchip/9aedfb528600ecf871885f7293ca4207c84d16c1.camel@gmail.com/
Reported-by: <aleksandr.o.makarov@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210928143413.v3.1.Ic2904d37f30013a7f3d8476203ad3733c186827e@changeid