wr_gtx_phy_kintex7_lp: fixed DMTD configuration to match new clock frequencies, more control over resets

wr_si57x_interface: latch the current RFREQ value before writing it to the device (prevents changes of the RFREQ while I2C is still busy)

wr_board_pkg: declare eb_ethernet_slave as a component so that compiler doesn't complain when EB repo is not included