scsi: wd33c93: Replace deprecated strncpy() with strscpy()

scsi: wd33c93: Replace deprecated strncpy() with strscpy()

@p1 is assigned to @setup_buffer and then we manually assign a NUL-byte at
the first index. This renders the following strlen() call useless.
Moreover, we don't need to reassign p1 to setup_buffer for any reason --
neither do we need to manually set a NUL-byte at the end. strscpy()
resolves all this code making it easier to read.

Even considering the path where @str is falsey, the manual NUL-byte
assignment is useless as setup_buffer is declared with static storage
duration in the top-level scope which should NUL-initialize the whole
buffer.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240305-strncpy-drivers-scsi-mpi3mr-mpi3mr_fw-c-v3-7-5b78a13ff984@google.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>