net: ravb: Rely on PM domain to enable gptp_clk

net: ravb: Rely on PM domain to enable gptp_clk

ravb_rzv2m_hw_info::gptp_ref_clk is enabled only for RZ/V2M. RZ/V2M
is an ARM64-based device which selects power domains by default and
CONFIG_PM. The RZ/V2M Ethernet DT node has proper power-domain binding
available in device tree from the commit that added the Ethernet node.
(4872ca1f92b0 ("arm64: dts: renesas: r9a09g011: Add ethernet nodes")).

Power domain support was available in the rzg2l-cpg.c driver when the
Ethernet DT node has been enabled in RZ/V2M device tree.
(ef3c613ccd68 ("clk: renesas: Add CPG core wrapper for RZ/G2L SoC")).

Thus, remove the explicit clock enable for gptp_clk (and treat it as the
other clocks are treated) as it is not needed and removing it doesn't
break the ABI according to the above explanations.

By removing the enable/disable operation from the driver we can add
runtime PM support (which operates on clocks) w/o the need to handle
the gptp_clk in the Ethernet driver functions like ravb_runtime_nop().
PM domain does all that is needed.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>