media: s5p-g2d: Fix a memory leak on ctx->fh.m2m_ctx

The m2m_ctx resources was allocated by v4l2_m2m_ctx_init() in g2d_open()
should be freed from g2d_release() when it's not used.

Fix it

Fixes: 91884734 ("[media] v4l: add G2D driver for s5p device family")
Signed-off-by: Dillon Min <dillon.minfei@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>