net: ravb: Avoid unsupported internal delay mode for R-Car E3/D3

According to the R-Car Gen3 Hardware Manual Rev 1.50 of Nov 30, 2018, the
TX clock internal delay mode isn't supported on R-Car E3 (r8a77990) or D3
(r8a77995).

Avoid setting the APSR:TDM bit on these SoCs. Moreover, only set APSR:TDM
when the DT explicitly specifies RGMII ID or TXID mode instead of setting
it unconditionally when the PHY link speed is 1000 Mbit/s.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Cc: Joe Hershberger <joe.hershberger@ni.com>