drm: bridge: dw-hdmi: Assert SVSRET before resetting the PHY

According to the PHY IP core vendor, the SVSRET signal must be asserted
before resetting the PHY. Tests on RK3288 and R-Car Gen3 showed no
regression, the change should thus be safe.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170117082910.27023-20-laurent.pinchart+renesas@ideasonboard.com