OMAP: DSS2: Renaming register macro DISPC_DIVISOR(ch)

The OMAP4 DISPC_DIVISOR1 is backward compatible to OMAP3xxx DISPC_DIVISOR.
However DISPC_DIVISOR is also provided in OMAP4, to control DISPC_CORE_CLK
independent of Primary and Secondary display clocks.

Renamed DISPC_DIVISOR(ch) to DISPC_DIVISORo(ch), to facilitate introduction
of DISPC_DIVISOR register, which is specific for OMAP4. OMAP4 has 3 registers
DISPC_DIVISOR, DISPC_DIVISOR1 and DISPC_DIVISOR2.

Also updated, all the usages of DISPC_DIVISOR(ch) to DISPC_DIVISORo(ch).
Use DISPC_DIVISORo(ch) when DISPC_DIVISOR1 or DISPC_DIVISOR2 has to be
configured

OMAP4 TRM uses DISPC_DIVISORo generically to refer to DISPC_DIVISOR1 and
DISPC_DIVISOR2

Signed-off-by: Raghuveer Murthy <raghuveer.murthy@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>