video: fbdev: nvidiafb: Use strscpy() to prevent buffer overflow

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

video: fbdev: nvidiafb: Use strscpy() to prevent buffer overflow

Coverity complains of a possible buffer overflow. However,
given the 'static' scope of nvidia_setup_i2c_bus() it looks
like that can't happen after examiniing the call sites.

CID 19036 (#1 of 1): Copy into fixed size buffer (STRING_OVERFLOW)
1. fixed_size_dest: You might overrun the 48-character fixed-size string
chan->adapter.name by copying name without checking the length.
2. parameter_as_source: Note: This defect has an elevated risk because the
source argument is a parameter of the current function.
89 strcpy(chan->adapter.name, name);

Fix this warning by using strscpy() which will silence the warning and
prevent any future buffer overflows should the names used to identify the
channel become much longer.