media: vidtv: fix pass-by-value structs causing MSAN warnings

In the Linux kernel, the following vulnerability has been resolved: media: vidtv: fix pass-by-value structs causing MSAN warnings vidtv_ts_null_write_into() and vidtv_ts_pcr_write_into() take their argument structs by value, causing MSAN to report uninit-value warnings. While only vidtv_ts_null_write_into() has triggered a report so far, both functions share the same issue. Fix by passing both structs by const pointer instead, avoiding the stack copy of the struct along with its MSAN shadow and origin metadata. The functions do not modify the structs, which is enforced by the const qualifier.