netxen_nic: Use {low,upp}er_32_bits() helpers

Use the existing {low,upp}er_32_bits() helpers instead of defining
custom variants.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/319d4a5313ac75f7bbbb6b230b6802b18075c3e0.1720430602.git.geert+renesas@glider.be


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