doc: replace @return by Return:

Sphinx expects Return: and not @return to indicate a return value.

find . -name '*.c' -exec \
sed -i 's/^\(\s\)\*\(\s*\)@return\(\s\)/\1*\2Return:\3/' {} \;

find . -name '*.h' -exec \
sed -i 's/^\(\s\)\*\(\s*\)@return\(\s\)/\1*\2Return:\3/' {} \;

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

net/eth_internal.h

@@ -22,7 +22,7 @@ void eth_common_init(void);
  * @base_name:	Base name for variable, typically "eth"
  * @index:	Index of interface being updated (>=0)
  * @enetaddr:	Pointer to MAC address to put into the variable
- * @return 0 if OK, other value on error
+ * Return: 0 if OK, other value on error
  */
 int eth_env_set_enetaddr_by_index(const char *base_name, int index,
 				 uchar *enetaddr);