index: remove file-scope entry size macros

All index entry size computations are now performed in
`index_entry_size`. As such, we do not need the file-scope macros for
computing these sizes anymore. Remove them and move the `entry_size`
macro into the `index_entry_size` function.
diff --git a/src/index.c b/src/index.c
index 820c971..ed9f478 100644
--- a/src/index.c
+++ b/src/index.c
@@ -54,10 +54,6 @@
 				  unsigned int flags,
 				  git_index_matched_path_cb cb, void *payload);
 
-#define entry_size(type,len) ((offsetof(type, path) + (len) + 8) & ~7)
-#define short_entry_size(len) entry_size(struct entry_short, len)
-#define long_entry_size(len) entry_size(struct entry_long, len)
-
 #define minimal_entry_size (offsetof(struct entry_short, path))
 
 static const size_t INDEX_FOOTER_SIZE = GIT_OID_RAWSZ;
@@ -2290,10 +2286,12 @@
 		else
 			return offsetof(struct entry_short, path) + path_len + 1 + varint_len;
 	} else {
+#define entry_size(type,len) ((offsetof(type, path) + (len) + 8) & ~7)
 		if (flags & GIT_IDXENTRY_EXTENDED)
-			return long_entry_size(path_len);
+			return entry_size(struct entry_long, path_len);
 		else
-			return short_entry_size(path_len);
+			return entry_size(struct entry_short, path_len);
+#undef entry_size
 	}
 }