realtek: dsa: rtl930x: Fix flow control with ingress shaping

realtek: dsa: rtl930x: Fix flow control with ingress shaping

Tests with ingress shaping and enabled flow control showed really high
packet loss. It seems like the MAC pause frames are not created correctly
when both burst high off is set to the same value as burst high on.

By default, RTL930x has set the burst high values to:

* on: 64K
* off: 32K

Using the same 1:2 ratio seems to solve the high packet loss rate during
UDP tests.

Fixes: 2e74eb6d93a7 ("realtek: dsa: rtl93xx: Support per port throttling")
Signed-off-by: Sven Eckelmann <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/21011
Signed-off-by: Robert Marko <[email protected]>