media: staging: atomisp: use kstrdup to replace kmalloc and memcpy

kstrdup kernel primitive can be used to replace kmalloc followed by
string copy. This was reported by coccinelle tool.

Signed-off-by: Hari Prasath <gehariprasath@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>