net: stmmac: mostly remove "buf_sz"

net: stmmac: mostly remove "buf_sz"

The "buf_sz" parameter is not used in the stmmac driver - there is one
place where the value of buf_sz is validated, and two places where it
is written. It is otherwise unused.

Remove these accesses. However, leave the module parameter in place as
removing it could cause module load to fail, breaking user setups.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Furong Xu <0x1207@gmail.com>
Link: https://patch.msgid.link/E1tpswn-005U6I-TU@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>