omap4: dpll: Enable auto gate control for all MX postdividers

Enable hardware gate control for all dpll MX and X2 postdividers.
This requires the allow_idle/deny_idle functions to be
populated for all clock nodes (mx/x2 post dividers) in
clkops.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>