r8169: increase max jumbo packet size on RTL8125/RTL8126

r8169: increase max jumbo packet size on RTL8125/RTL8126

Realtek confirmed that all RTL8125/RTL8126 chip versions support up to
16K jumbo packets. Reflect this in the driver.

Tested by Rui on RTL8125B with 12K jumbo packets.

Suggested-by: Rui Salvaterra <rsalvaterra@gmail.com>
Tested-by: Rui Salvaterra <rsalvaterra@gmail.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/396762ad-cc65-4e60-b01e-8847db89e98b@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>