coda: Avoid partial allocation of sig_inputArgs

GCC does not like having a partially allocation object, since it cannot reason about it for bounds checking when it is passed to other code. Instead, fully allocate sig_inputArgs. (Alternatively, sig_inputArgs should be defined as a struct coda_in_hdr, if it is actually not using any other part of the union.) Seen under GCC 13:

../fs/coda/upcall.c: In function 'coda_upcall':
../fs/coda/upcall.c:801:22: warning: array subscript 'union inputArgs[0]' is partly outside array bounds of 'unsigned char[20]' [-Warray-bounds=]
801 | sig_inputArgs->ih.opcode = CODA_SIGNAL;
| ^~

---
 fs/coda/upcall.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 59f6cfd06f96..cd6a3721f6f6 100644
@@ -791,7 +791,7 @@ static int coda_upcall(struct venus_comm *vcp,
 	sig_req = kmalloc(sizeof(struct upc_req), GFP_KERNEL);
 	if (!sig_req) goto exit;
 
-	sig_inputArgs = kvzalloc(sizeof(struct coda_in_hdr), GFP_KERNEL);
+	sig_inputArgs = kvzalloc(sizeof(*sig_inputArgs), GFP_KERNEL);
 	if (!sig_inputArgs) {
 		kfree(sig_req);
 		goto exit;

2.34.1