board: ti: dra71x-evm: Add epprom support

The dra71x-evm is a board based on TI's DRA718 processor targeting BOM-optimized
entry infotainment systems such as display audio and is a software compatible
derivative of the highly successful DRA74 and DRA72 processor families.
More information can be found here[1].

Add epprom detection for dra71-evm.

[1] http://www.ti.com/product/dra718



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