ARM: davinci: clk framework support for enable/disable functionality

DaVinci clock implementation does not support clock enable/disable
functionality on non-PSC clock nodes.

On DA850 SoC, EHRPWM module requires support for enable/disable
of TBCLK controlled using a system module register.

This patch adds a method for enabling/disabling non-PSC clocks
into DaVinci clock implementation.

Signed-off-by: Philip Avinash <avinashphilip@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>