ARM: OMAP4+: Add support for getting pbias info from board

Palmas driver assumes it is always TPS659xx regulator on all DRA7xx based
boards to enable mmc regulator. This is not true always like in case of
DRA71x-evm. So get this information based on the board.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
[trini: Delete omap4_vmmc_pbias_config from omap_hsmmc.c]
Signed-off-by: Tom Rini <trini@konsulko.com>