While replacing strncpy() with strscpy(), Bart Van Assche pointed out
that the code occurs inside sysfs write callbacks, which already uses
NUL-terminated strings. This allows the string to be passed directly to
sscanf() without requiring a temporary copy.
Remove the deprecated and unnecessary strncpy() and the corresponding
local variables, and pass the buffer buf directly to sscanf().
Replace sscanf() with kstrtoint() to silence checkpatch warnings.