There are few list handling issues while adding and deleting
node in the registered buf list in the driver.
1. list addition - buffer added into the list during buf_init
while not deleted during cleanup.
2. list deletion - In capture streamoff, the list was reinitialized.
As a result, if any node was present in the list, it would
lead to issue while cleaning up that node during buf_cleanup.

Corresponding call traces below:
[  165.751014] Call trace:
[  165.753541]  __list_add_valid+0x58/0x88
[  165.757532]  venus_helper_vb2_buf_init+0x74/0xa8 [venus_core]
[  165.763450]  vdec_buf_init+0x34/0xb4 [venus_dec]
[  165.768271]  __buf_prepare+0x598/0x8a0 [videobuf2_common]
[  165.773820]  vb2_core_qbuf+0xb4/0x334 [videobuf2_common]
[  165.779298]  vb2_qbuf+0x78/0xb8 [videobuf2_v4l2]
[  165.784053]  v4l2_m2m_qbuf+0x80/0xf8 [v4l2_mem2mem]
[  165.789067]  v4l2_m2m_ioctl_qbuf+0x2c/0x38 [v4l2_mem2mem]
[  165.794624]  v4l_qbuf+0x48/0x58

[ 1797.556001] Call trace:
[ 1797.558516]  __list_del_entry_valid+0x88/0x9c
[ 1797.562989]  vdec_buf_cleanup+0x54/0x228 [venus_dec]
[ 1797.568088]  __buf_prepare+0x270/0x8a0 [videobuf2_common]
[ 1797.573625]  vb2_core_qbuf+0xb4/0x338 [videobuf2_common]
[ 1797.579082]  vb2_qbuf+0x78/0xb8 [videobuf2_v4l2]
[ 1797.583830]  v4l2_m2m_qbuf+0x80/0xf8 [v4l2_mem2mem]
[ 1797.588843]  v4l2_m2m_ioctl_qbuf+0x2c/0x38 [v4l2_mem2mem]
[ 1797.594389]  v4l_qbuf+0x48/0x58
Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>
Reviewed-by: Fritz Koenig <frkoenig@chromium.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>