nouveau/svm: Replace one-element array with flexible-array member in struct nouveau_svm

nouveau/svm: Replace one-element array with flexible-array member in struct nouveau_svm

One-element and zero-length arrays are deprecated. So, replace
one-element array in struct nouveau_svm with flexible-array member.

This results in no differences in binary output.

Link: https://github.com/KSPP/linux/issues/338
Signed-off-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/087a1c335228bd245192bbb2fb347c9af1be5750.1692208802.git.gustavoars@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>