clk: imx7d: do not set parent of ethernet time/ref clocks

All device trees currently in mainline specify the time clock parent
using the assigned-clocks/assigned-clock-parents method, there is no
need to statically assign the parent in the core clock driver.
Also all current boards provide an Ethernet reference clock for the
PHY externally, hence configuring the internal PHY reference clock.

Furthermore, and the actual driver of this patch, specify ethernet
related parents at that early point in boot leads to a warning:
bad: scheduling from the idle thread!

The reason for the warning is that setting the parent enables the ENET
PLL since we are using CLK_OPS_PARENT_ENABLE. Enabling the ENET PLL can
cause clk_pllv3_wait_lock to sleep. See also:
commit fc8726a2 ("clk: core: support clocks which requires parents
enable (part 2)").

Note that setting the ENET AXI root clock parent also requires ENET
PLL to be enabled. However, U-Boot typically leaves the ENET PLL on,
hence when the framework sets the parent of the first clock, it does
not need to wait for the PLL to come up. But because there is currently
no user of that clock, the PLL gets disabled after setting the parent.
Therefore, subsequent reparenting calls of any clock which somehow rely
on the ENET PLL, need to reenable the ENET PLL which leads to a sleep.
Removing those subsequent reparenting calls works around this issue.

Also remove comments. The code is really verbose enough.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Tested-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/20160703174813.13970-1-stefan@agner.ch