drm/vc4: crtc: Remove redundant pixelvalve reset

Since we moved the pixelvalve configuration to atomic_enable, we're now
first calling the function that resets the pixelvalve and then the one that
configures it.

However, the first thing the latter is doing is calling the reset function,
meaning that we reset twice our pixelvalve. Let's remove the first call.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a0a31af0d4a7a070de979f0e5b618d9e2c730e7f.1599120059.git-series.maxime@cerno.tech