am57xx_hs_evm_usb: Enable AHCI and BLK

Enable the AHCI and BLK features to complete migration of various
drivers.

Cc: Andrew F. Davis <afd@ti.com>
Cc: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tom Rini <trini@konsulko.com>