omap_hsmmc: Board-specific TWL4030 MMC power initializations

omap_hsmmc: Board-specific TWL4030 MMC power initializations

Boards using the TWL4030 regulator may not all use the LDOs the same way
(e.g. MMC2 power can be controlled by another LDO than VMMC2).
This delegates TWL4030 MMC power initializations to board-specific functions,
that may still call twl4030_power_mmc_init for the default behavior.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@ti.com>
[trini: Fix omap3_evm warning, add twl4030.h]
Signed-off-by: Tom Rini <trini@ti.com>