media: meson: vdec: remove redundant if statement

Checking if sess->fmt_out->pixfmt is V4L2_PIX_FMT_VP9 was already done as a
condition to enter the if statement where this additional check is made.

Signed-off-by: Benjamin Roszak <benjamin545@gmail.com>
Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>