board: ti: dra72: Introduce optimization for rgmii timing for rev C

Rev C version of EVM does require IODelay to be configured for RGMII
pins in MANUAL_1 configuration. Update the same based on PG2.0 initial
simulation values.
Data based on PCT_DRA72x_SR2.0_SR1.0_v1.3.0.7

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