OMAP3 clock: convert dpll_data.idlest_bit to idlest_mask

Convert struct dpll_data.idlest_bit field to idlest_mask.  Needed since
later patches are converting the DPLL bypass state test to use the IDLEST
registers, and OMAP2 uses two bits for DPLL IDLEST rather than one.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>