CVE-2022-49478

In the Linux kernel, the following vulnerability has been resolved:

media: pvrusb2: fix array-index-out-of-bounds in pvr2_i2c_core_init

Syzbot reported that -1 is used as array index. The problem was in
missing validation check.

hdw->unit_number is initialized with -1 and then if init table walk fails
this value remains unchanged. Since code blindly uses this member for
array indexing adding sanity check is the easiest fix for that.

hdw->workpoll initialization moved upper to prevent warning in
__flush_work.