board: ti: dra71x-evm: Add PMIC support

Add the pmic_data for LP873x PMIC which is used to power
up dra71x-evm.

Note: As per the DM[1] DRA71x supports only OP_NOM. So, updating
the efuse registers only to use OPP_NOM irrespective of any
CONFIG_DRA7_<VOLT>_OPP_{NOM,od,high} is defined.

[1] http://www.ti.com/product/DRA718/technicaldocuments



Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>