generic: add fix for AQR113 PMD Global Transmit Disable bit

generic: add fix for AQR113 PMD Global Transmit Disable bit

PMD Global Transmit Disable bit should be cleared for normal operation.
This should be HW default, however I found that on Asus RT-AX89X that uses
AQR113C PHY and firmware 5.4 this bit is set by default.

With this bit set the AQR cannot achieve a link with its link-partner and
it took me multiple hours of digging through the vendor GPL source to find
this out, so lets always clear this bit during .config_init() to avoid a
situation like this in the future.

aqr107_wait_processor_intensive_op() is moved up because datasheet notes
that any changes to this bit are processor intensive.

This is a modified version of patch that got merged upstream as AQR113C
has a separate config_init() upstream.

Link: https://github.com/openwrt/openwrt/pull/15840
Signed-off-by: Robert Marko <robimarko@gmail.com>