[U-Boot] [PATCH v4 0/3] mmc: Board-specific MMC power initializations

Changelog:

v4: * Switch board_mmc_power_init to void since there is no return value check * Add dev_index to twl4030_power_mmc_init, common ramp-up delay * twl4030_power_mmc_init call with the relevant dev_index on boards * No check against CONFIG_TWL4030_POWER (an obvious linker error is better than a strange runtime error)

v3: Changes to make v2 apply on master

v2: Implement board_mmc_power_init instead of define