crypto: octeontx2 - Call strscpy() with correct size argument

In otx2_cpt_dl_custom_egrp_create(), strscpy() is called with the length
of the source string rather than the size of the destination buffer.

This is fine as long as the destination buffer is larger than the source
string, but we should still use the destination buffer size instead to
call strscpy() as intended. And since 'tmp_buf' is a fixed-size buffer,
we can safely omit the size argument and let strscpy() infer it using
sizeof().

Fixes: d9d77497 ("crypto: octeontx2 - add apis for custom engine groups")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>