alpha: Replace one-element array with flexible-array member

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

This results in no differences in binary output.
Signed-off-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/ZMpZZBShlLqyD3ax@workSigned-off-by: Kees Cook <keescook@chromium.org>

arch/alpha/kernel/osf_sys.c

@@ -97,7 +97,7 @@ struct osf_dirent {
 	unsigned int d_ino;
 	unsigned short d_reclen;
 	unsigned short d_namlen;
-	char d_name[1];
+	char d_name[];
 };
 
 struct osf_dirent_callback {