msgbuf: Return -EOVERFLOW where relevant in pldm_msgbuf_consumed()

-EBADMSG seems less appropriate for access patterns known to exceed
buffer limits.

Change-Id: I3051323cad0ec126c0fe5073902fcc50f8ff18a0
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
diff --git a/tests/msgbuf.cpp b/tests/msgbuf.cpp
index bb64be9..14f5d73 100644
--- a/tests/msgbuf.cpp
+++ b/tests/msgbuf.cpp
@@ -516,7 +516,7 @@
     ASSERT_EQ(pldm_msgbuf_init_errno(ctx, 0, buf, sizeof(buf)), 0);
     EXPECT_EQ(pldm_msgbuf_extract_uint8(ctx, valid), 0);
     EXPECT_NE(pldm_msgbuf_extract_uint8(ctx, invalid), 0);
-    EXPECT_EQ(pldm_msgbuf_complete_consumed(ctx), -EBADMSG);
+    EXPECT_EQ(pldm_msgbuf_complete_consumed(ctx), -EOVERFLOW);
 }
 
 TEST(msgbuf, pldm_msgbuf_insert_int32_good)