net: dsa: tag_rtl4_a: Drop bit 9 from egress frames

This drops the code setting bit 9 on egress frames on the
Realtek "type A" (RTL8366RB) frames.

This bit was set on ingress frames for unknown reason,
and was set on egress frames as the format of ingress
and egress frames was believed to be the same. As that
assumption turned out to be false, and since this bit
seems to have zero effect on the behaviour of the switch
let's drop this bit entirely.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20210913143156.1264570-1-linus.walleij@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>