media: media/dvb: Use kmemdup rather than duplicating its implementation

mainline inclusion
from mainline-v5.4-rc1
commit f6af820e
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I635IG
CVE: CVE-2022-45884

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f6af820ef1be58c2e4b81aa479b9f109eb6344ce



---------------------------

kmemdup is introduced to duplicate a region of memory in a neat way.
Rather than kmalloc/kzalloc + memcpy, which the programmer needs to
write the size twice (sometimes lead to mistakes), kmemdup improves
readability, leads to smaller code and also reduce the chances of mistakes.
Suggestion to use kmemdup rather than using kmalloc/kzalloc + memcpy.

Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: liwei <liwei728@huawei.com>