mx31_clocks_init() has been used to register clocks on i.MX31
non-devicetree platforms.

Now that i.MX is a devicetree-only platform, it is safe to
remove mx31_clocks_init() as there are no more users.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>