drm/mcde: Fix unbalanced regulator

Since we now turn off the EPOD regulator to reset the
hardware, we need to balance the regulators after that
point. If registering the master fails we only need
to disable one regulator. Fix this by open-coding
this leg of the error path.

Fixes: c4842d4d

 ("drm/mcde: Fix display pipeline restart")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Stephan Gerhold <stephan@gerhold.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20201108113535.1819952-1-linus.walleij@linaro.org