video: fbdev: simplefb: Separate clk / regulator get and enable steps

Currently when a simplefb needs both clocks and regulators and one
of the regulators returns -EPROBE_DEFER when we try to get it, we end
up disabling the clocks. This causes the screen to go blank; and in some
cases my cause hardware state to be lost resulting in the framebuffer not
working at all.

This commit splits the get and enable steps and only enables
clocks and regulators after successfully getting all of them,
fixing the disabling of the clocks which were left enabled by
the firmware setting up the simplefb.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>