net: broadcom: use ethtool string helpers

The latter is the preferred way to copy ethtool strings.

Avoids manually incrementing the pointer. Cleans up the code quite well.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20241104205317.306140-1-rosenp@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>