net: stmmac: Enable RX parameter configuration from device tree

Enabling RX configurations like rx_dll_bypass and rx_prog_swap
valies to be configured from device tree to support multiple
platforms.

Change-Id: I851b07563fbdf5eab9a4c15b773cacdb6b93c952
Signed-off-by: Aditya Mathur <aditmath@codeaurora.org>