ARM: davinci: dm646x: Remove legacy clock init

This removes the unused legacy clock init code from
arch/arm/mach-davinci/dm646x.c.

Signed-off-by: David Lechner <david@lechnology.com>
Reviewed-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>