s5p-mfc: Add handling of buffer freeing reqbufs

In encoder, the count of reqbufs is zero, will would free the
buffers but it won't make the state of encoder wrong, this patch
may fix this problem. This main backport from chromiumos.
s5p-mfc: set default MAX QP value for encoder

Rate control when enabled, target bitrate is achieved
through adaptively adjusting the QP between the min and
max values set by the driver.

Fow H264 encoder, fix the default MAX QP value to 51, which
is the maximum value QP can take. Now, MFC starts with a QP
set using V4L2_CID_MPEG_VIDEO_H264_I_FRAME_QP and adapts to
achieve the target bitrate.

similarly, default MAX QP values are modified for h263 and
mpeg4 encoders

BUG=chrome-os-partner:18019
BUG=chrome-os-partner:21917
TEST=build, run mfc encoder on CrOS pit
backport from the above.
s5p-mfc： add G_MIN_BUFFERS
remove some binary file

They shouldn't be in here.