OMAP4: scale voltage of core before MPU scales

OMAP4: scale voltage of core before MPU scales

OMAP4 requires that parent domains scale ahead of dependent domains.
This is due to the restrictions in timing closure. To ensure
a consistent behavior across all OMAP4 SoC, ensure that
vdd_core scale first, then vdd_mpu and finally vdd_iva.

As part of doing this refactor the logic to allow for future
addition of OMAP4470 without much ado. OMAP4470 uses different
SMPS addresses and cannot be introduced in the current code
without major rewrite.

Reported-by: Isabelle Gros <i-gros@ti.com>
Reported-by: Jerome Angeloni <j-angeloni@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>