usb: dwc3-am62: fix module unload/reload behavior

In the Linux kernel, the following vulnerability has been resolved:

usb: dwc3-am62: fix module unload/reload behavior

As runtime PM is enabled, the module can be runtime

suspended when .remove() is called.

Do a pm_runtime_get_sync() to make sure module is active

before doing any register operations.

Doing a pm_runtime_put_sync() should disable the refclk

so no need to disable it again.

Fixes the below warning at module removel.

[ 39.705310] ------------[ cut here ]------------

[ 39.710004] clk:162:3 already disabled

[ 39.713941] WARNING: CPU: 0 PID: 921 at drivers/clk/clk.c:1090 clk_core_disable+0xb0/0xb8

We called of_platform_populate() in .probe() so call the

cleanup function of_platform_depopulate() in .remove().

Get rid of the now unnnecessary dwc3_ti_remove_core().

Without this, module re-load doesn't work properly.