realtek: eth: introduce global interrupt helpers

realtek: eth: introduce global interrupt helpers

Global interrupt enabling/disabling is scattered around the code. Provide
two helpers to handle this code centrally. Make use of them where needed.
This refactoring brings multiple enhancements:

1. Only activate the rx interrupts and ignore the run out (aka rx overflow)
interrupts. Overflow was used to spit out log messages to identify driver
issues. Nowadays it is stable enough and these messages are not needed
any longer.

2. With generic register setting some family checks can be dropped.

3. Last but not least this commit fixes a bug in the probing of the ethernet
driver. In rare case (especially during TFTP boot) U-Boot loader leaves a
pending rx interrupt that instantly fires when the driver registers its
interrupt via devm_request_irq(). To mitigate this, reorder the interrupt
disabling from ndo_open() to driver probing.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/21893
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>